Department of Computer Science

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Research Overview of the Computer Science Department This brochure gives an overview of the ongoing research activities at the Department of Computer Science of ETH Zurich. It is a collection of the two-page research summaries given by every professor of the Department. The following pages are in alphabetical order of the names of the professors.

Gustavo Alonso Information and Communication Systems Research Group Armin Biere Formal Methods for Solving Complexity and Quality Problems Walter Gander From Numerical Analysis to Scientific Computing Gaston Gonnet Computational Biochemistry and Computer Algebra Markus Gross Computer Graphics Laboratory Thomas Gross Laboratory for Software Technology Jürg Gutknecht Program Languages and Runtime Systems Petros Koumoutsakos Computational Sciences Friedemann Mattern Ubiquitous Computing Infrastructures Ueli Maurer Information Security and Cryptography Bertrand Meyer Chair of Software Engineering Kai Nagel Modeling and Simulation Jürg Nievergelt Algorithms, Data Structures, and Applications Moira Norrie Constructing Global Information Spaces Hans-Jörg Schek Realizing the Hyperdatabase Vision Bernt Schiele Perceptual Computing and Computer Vision Robert Stärk Computational Logic Thomas Stricker Parallel- and Distributed Systems Group Roger Wattenhofer Distributed Computing Group Emo Welzl Theory of Combinatorial Algorithms Peter Widmayer Algorithms, Data Structures, and Applications Carl August Zehnder Development and Application Group

The most up-to-date research summaries can be found under Û research in the Web presentation of the Department. This version is as of June 12, 2002. Information and Communication Systems Research Group

Information Systems Prof. Gustavo Alonso

http://www.inf.ethz.ch/department/IS/iks/ [email protected]

Figure 1 to 4 BiOpera, a development and run time environment for cluster and grid computing

The motivation behind our research uted at a large scale and heterogeneous. Thus, much of our Computers and networks are pervasive. In the new millennium, research goes into building the core middleware infrastructure both will play an ever increasing and decisive role in all human needed to cope with the new communication environments: endeavors. By exploring and striving to understand the oppor- wireless, nomadic, ubiquitous, multi-hop, ad-hoc, etc. We also tunities offered by the synergy between information and com- use these core middleware systems to develop real applica- munication technology, our research is contributing to turn tions, thereby making useful contributions while obtaining such technologies into the very fabric of society. Progressing important feedback for our long term research goals. towards a true information and communication society, however, involves more than producing faster, more efficient, or Large scale distributed computing new technologies. The real breakthrough will be when we One of our main research projects is a development and run- finally learn to build software systems that are less intrusive, time environment for the specification, execution, and moni- less prone to failures, and better tailored to the user’s needs. toring of complex sequences of application invocations in dis- Our work aims at overcoming the many obstacles we face in tributed environments. Such systems are likely to become a key building such systems. First, in our research, by solving a wide building block of corporate IT infrastructures, software devel- variety of scientific and engineering problems. Second, in terms opment environments, and scientific computing since they proof education, by motivating and teaching students to explore vide the services necessary to integrate distributed, heteroge- new approaches to software development, systems architec- neous applications into a coherent whole. The system currently ture and systems integration. available, OPERA, is a generic kernel that combines research interest with practical constraints in terms of efficiency, scala- Our research bility, easy-of-use, and fault tolerance. We have already used In our search for the recipe for better software systems, we are OPERA to implement several real applications. One of them is a exploring a wide range of application scenarios. We work at all platform for electronic commerce (WISE) that has been adopt- levels of the software hierarchy: from programming languages ed by several companies. Our most recent effort is to create a to user interfaces, including communication protocols, data computing grid with OPERA as the basic middleware. storage, and system properties like scalability, performance, or persistence. We also believe that future systems will be distrib- Information and Communication Systems Research Group Prof. Gustavo Alonso

Gustavo Alonso was born Research Center before in Madrid, Spain in 1965. joining ETH in 1995. In 1998 He holds a degree in he became an Assistant Telecommunication Professor for Computer engineering from the Science and since then Universidad Politecnica de leads the Information and Madrid (1989), and a M.S. Communication Systems (1992) and a Ph.D. (1994) in Research Group. Computer Science from the University of California at Santa Barbara. He worked at the IBM Almaden

Figure 6 to 7 Full resolution image of a solar flare (above) and its low resolution counterpart (below). The low resolution image is very similar to the original and yet much more efficient to store and compute

Applications in ad-hoc environments Browsing terabytes of scientific data Novel computing environments like mobile ad-hoc networks Most scientific applications reflect the still widespread percep- (MAHNs) are challenging our understanding of software design. tion that software development can be effectively done in an To support these new computing environments, we need to ad-hoc manner and without proper training. This perception is abandon the traditional paradigm whereby software capabili- the more surprising given that such applications are today ties are determined at build time. Indeed, when the ability to among the most complex challenges faced by information and react to changes or new environments is encoded in an appli- communication technology. We are committed to change this cation before it is deployed, the flexibility of that application is perception through education. We are also participating in a quite limited. Worse still, the mere fact that the application number of projects where we are developing scientific tools carries its own code for adaptation makes it more complex using modern software techniques. Our goal is to come up and, therefore, more difficult to maintain and evolve. The self- with generic solutions that can be applied to a wide range of organizing nature of the communication environment sug- problems and are not just a one-time programming effort. gests a possible solution to this problem. What is needed is to As an example of these efforts, we are building a data center treat functionality as a dynamic property so that applications for a NASA satellite. The center provides tools for browsing can be adapted at run-time. Following this idea, we are build- approximated data, performing low-resolution analysis, and ing the infrastructure necessary to allow software applications synchronization of client caches with the server and among capable of self-organization. Instead of establishing before- peers. It also offers several innovative interfaces to allow users hand what an application can and cannot do, we propose to to efficiently peruse large amounts of data. let applications that meet in an ad-hoc fashion to exchange The most interesting aspect of these tools is that, although and adapt their functionality in order to pursue their common quite innovative in themselves, they can be used with many goal. We have a first prototype, PROSE, that enables self-orga- other types of scientific data, thereby providing scientist the nization. It is based on a run-time aspect oriented tool for Java type of reuse and standard development platforms common to virtual machines. We are also working on a number of applica- the IT world. tion scenarios including ad-hoc containers and Jini based robots capable of self-organization. Formal Methods for Solving Complexity and Quality Problems

Computer Systems Group Formal Methods Prof. Armin Biere

http://www.inf.ethz.ch/~biere/ [email protected]

Motivation Computer systems developed today are becoming increasingly complex, and can no longer be reasonably mastered by conventional methods. Despite consistent use of classical testing and validation technologies, the quality of new systems is often insufficient. In order to keep quality on a tolerable level, projects may have to deal with missed deadlines. In some case even the entire project has to be canceled due to quality problems. On the other hand, computer systems are becoming ubiquitous in our daily lives. This increases everyone’s dependency on computer systems. Even our life itself depends on the correct functioning of such systems (e.g., steer-by-wire). In this context, quality problems are unac- ceptable. Under this premise, only those who understand quality assurance as an integral part of systems engineering will survive international com- petition. This applies to companies as well as educational institutions! As a first step, reflection and professionalization of the development process as such, is gaining importance in the software industry. Quality measurement and repeatability are the decisive key words, independent of the application of formal methods. In the hardware industry and for embedded systems, such processes are already commonplace today. For obvious reasons, failures can be very expensive, and thus the search for reliable methods for quality assurance has begun much earlier than in the software world. Figure 1 In the face of accelerating technological progress, maintaining Binary Decision acceptable quality standards is very difficult. In the hardware commu- Diagrams (BDDs) can be used for compact nity the explosion of testing costs has become an almost unsolvable representation of problem. The insight, that Formal Methods are the only possible way boolean functions, for out of the quality dilemma, is gaining acceptance in the industry. instance the input/output relation of a 2 bit Hardware multiplier Therefore there is a tendency towards employing formal methods at almost all larger chip manufacturers. Initially technologies are Figure 1 absorbed, that can easily be integrated into existing development Equivalence checking of processes. This includes Equivalence Checking, where circuits are veri- combinational circuits fied for functional equivalence. Furthermore, Model Checking, where is the most successful application of formal temporal properties are examined, is gaining acceptance. methods in industry. The state space explosion with Model Checking is still the main problem of this technology. Therefore, increasing the capacity of Model Checking is one of the key issues. Bounded Model Checking, to which we made significant contributions, can handle larger systems. Therefore, it is getting established as a standard technology in the industry besides classical approaches based on Binary Decision Formal Methods for Complexity and Quality Problems Prof. Armin Biere

Prof. Armin Biere In 1997 he received the title Since April 2000 he is grew up in the Dr.rer.nat. from the Assistant Professor at ETH black forest, University of Karlsruhe for Zürich at the Institute of Germany. In 1987 his dissertation on efficient Computersystems. Figure 3 he started his studies in model checking of the His main interest is in As in system develop- Computer Science at the mu-calculus with binary applying formal methods ment in general the key University of Karlsruhe, decision diagrams. to realistic hardware and to successful application Germany, where he finished In 1997/1998 he continued software systems. of formal methods is a his undergraduate studies his research on model layered approach with with a Diploma in checking as a Postdoc with- stepwise refinement and Computer Science in 1993. in the group of Prof. E. verification. From 1993 to 1997 he Clarke at Carnegie Mellon worked on his Ph.D. with University in Pittsburgh PA. Prof. P. Deussen as super- Then he moved to the visor at the Institute for start-up company Verysys Logic, Complexity and Electronic Design Deductionsystems. Automation (Fremont CA and Berlin Germany) as Senior Technologist Model Checking.

Diagrams (BDDs). Further work in this area is very promising. Projects Formal Specification and Synthesis, can have the largest impact, Starting from mu-cke, an efficient finite state model checker for the potentially covering many phases in the development process. rich specification language mu-calculus, we worked on the implemen- However, this approach demands a complete adaptation of the exist- tation of various model checkers in academia and in industry. New ing development process, and therefore is struggling for acceptance in model checking algorithms and heuristics have been devised, and we the industry. contributed to the state-of-the-art of techniques for the implementa- In later stages of the process, Formal Specification and Synthesis tion of binary decision diagrams (BDDs). This data structure is at the already had astonishing success. The major part of the control soft- core of classical symbolic model checkers and in general plays a promi- ware of a new Airbus is being developed in Synchronous Languages. nent role in the design of digital circuits. These languages offer a high abstraction level and particularly allow In recent years we successfully worked on complementing the use formal treatment. Here, formal methods excel as a natural extension of of BDDs in symbolic model checking with technologies from Artificial the compilation idea: translating a specification into an implementa- Intelligence (AI), particularly satisfiability solvers (SAT). These tech- tion. niques make model checking much more robust, especially on larger In the long run, formal synthesis should be used on higher abstraction designs. We are working on combining SAT and BDDs to obtain even levels, where faults with the highest costs are introduced. An integrat- more powerful model checking algorithms. Another research project ed formal development process is the ultimate goal, with precisely along this line is the development of efficient algorithms for the satis- defined modeling languages on all levels, from requirements analysis fiability problem of Quantified Boolean Formulae (QBF), which, similar to concrete implementation. to the mu-calculus, represent a common framework for the solution of In order to support a developer using Formal Synthesis to the high- numerous verification and planning problems. est extent, an efficient verification technology is indispensable. Such Beside these projects, mainly focusing on hardware verification, we help is needed for the automation of synthesis steps and the integra- recently started to apply formal technology to software, where we ear- tion of formally verified components in a bottom-up manner. Existing lier worked on dynamic checkers only. In one project we statically approaches to Formal Synthesis, such as the B method and Abstract check large-scale Java programs for potential synchronization prob- State Machines (ASMs) are insufficient. lems. We investigate how this approach can be made even more precise, producing less spurious warnings. Other directions are the combi- Software nation of dynamic and static checking. Besides the application of Formal Methods to hardware, activities in Several case studies have been carried out, such as the verification software checking have increased as well. The new trend is the devel- of out-of-order processor designs and communication protocols. opment of tools which can treat large-scale industrial programs. This Currently we are looking into two-person games and financial applica- renaissance of program verification focuses on what is technically fea- tions. In general, we will continue to produce practical checking tools sible. It is motivated by significant gains in capacity of dedicated and apply them to realistic examples. analysis tools and theorem provers and the success story of Model Checking. In addition to software systems per se, systems including both hardware and software (Embedded Systems), are of primary interest in Switzerland. Our industry seminar has demonstrated, that especially Figure 4 there, the opportunities for applying Formal Methods are prevalent. Temporal Logic is the key The systems are rather small, compared to a formally verified leading for specifying sequential edge micro processor. Still they show enough characteristics of hard- behavior. Subtle difference between ware to make quality and thus Formal Methods one of the most various formalisms important factors in system development. exists. This example There will certainly be an increasing demand for know-how in discriminates linear and Formal Methods, particularly because of the quality dilemma discussed branching time temporal above. Academia has to serve this need with research and education. logics. From Numerical Analysis to Scientific Computing

Scientific Computing Prof. Walter Gander

http://www.inf.ethz.ch/personal/gander [email protected]

Computation of the optical properties of VCSELs Vertically-Cavity Surface-Emitting Lasers (VCSEL) are a new kind of lasers that are to be used for long-range optical signal transmission or for displays. One important subproblem in their design requires the solution of the time independent Maxwell equation for the electric field. Absorbing boundary conditions model the complete absorption of the light at the boundary. The finite element discretization leads to large matrix eigenvalue problems with complex-symmetric matrices. In this pro- Figure 1 and 2 Powerful and fast computer, new algorithms and intelli- ject we investigate eigensolvers and preconditioners Model cavity and ring cyclotron at Paul Scherrer gent software packages for computer algebra and that exploit this particular matrix structure (P. Arbenz Institute. numerical computing have changed the way we are and O. Chinellato). conducting research and teaching our students. Figure 3 Scientific computing and computational sciences are Swiss Food Composition Database Chinese edition the buzzwords used today to express the way to solve Information on the nutritional composition of foods of “Solving problems“ problems in science and engineering by simulation with is essential for the quantitative study of human nutri- the help of computers. Since about ten years our group tion, its application in the treatment and management and our institute plays an active role in this develop- of disease and the provision of appropriate diets for ment. individuals and populations. At the initiative of the Swiss Federal Office of Public Health a project was start- Research Projects ed to develop a food composition table paying special Software for Adaptive Quadrature attention to food available in Switzerland. The programs adaptsim and adaptlob developed by As part of this project we develop software for data W. Gander and W. Gautschi which were published in BIT, acquisition and compiling, data validation and quality have been incorporated in the new version of Matlab 6 control, calculating recipes of typical Swiss products. We and have replaced the former adaptive quadrature rou- also develop the computer science tools necessary to tines. manage and control the data. Prototypes are currently being used by the Institute of food science. A first Maxwell Eigenvalue Problems for Accelerating Cavities release is planned for the end of 2001 (H. Hinterberger) The design of accelerating cavities in a cyclotron requires the solution of very large sparse eigenvalue prob- Musac Figure 4 lems that are derived from finite element discretizations Musac is a software project to assist the determination MUSAC-Logo of the Maxwell equations that prevent spurious modes. of measurement uncertainty in analytical chemistry. We investigated numerous ways to solve the symmetric In order to satisfy the new ISO norms laboratories must positive semidefinite matrix eigenvalue problems. We indicate the combined measurement uncertainties developed highly efficient implementations of the sym- along with the measurement results. Musac calculates metric Jacobi-Davidson algorithm and variants of conju- the combined measurement uncertainty by auto- gate gradient-type eigensolvers. We investigate the use matically performing sensitivity analyses on model of various preconditioners to improve the performance descriptions of the measurement method at hand of the eigensolvers (P. Arbenz and R. Geus). (W. Gander and E. Achermann). From Numerical Analysis to Scientific Computing Prof. Walter Gander

Walter Gander is professor in the institute of scientific computing since 1987 and currently chairman of the department of computer Education science. Before his present appointment he was Walter Gander was member of the SIAM Working professor for numerical Group on Computational Science and Engineering analysis and computer Education and helped to define the curriculum for that science at the engineering field. He is also one of the fathers of the new curricu- college Neu-Technikum Buchs. His research interests lum for CSE at ETH. are: scientific computing, Our best seller, the book of Gander/Hrebicek: numerical linear algebra Solving Problems in Scientific Computing using Maple and parallel computing. and Matlab, Springer-Verlag, is being printed in 2001 in the fourth edition and has been translated to Chinese and Portuguese. Hans Hinterberger is involved in an education project called Information Processing for Domain Scientists. The goal of this project is to develop computer-supported interactive courseware to be used for Krylov Subspace Methods for Nonlinear Systems the instruction of first-year natural science students in of Equations the systematic use of computers to communicate, to In this project we combine ideas from vector extrapola- process scientific data and to manage information. tion methods with the ideas from linear Krylov subspace The instructional material shall support distance- and methods. Vector extrapolation methods are known to be time-independent learning and allow students to mathematically equivalent to linear Krylov subspace explore the different topics to a level of detail which methods. Unlike linear Krylov subspace methods they they can choose themselves, thereby providing an are also capable to solve nonlinear problems. However, opportunity for individualized learning The structure they lack numerical stability while linear Krylov sub- of the learning material shall be of a (modular) design space methods are stable. The goal of the project is that allows it to be readily adapted to engineering- to combine the ideas of these two concepts to get and business-oriented courses. numerically stable Krylov subspace methods for solving nonlinear systems of equations. These methods can be used on a wide range of applications, that result in Figure 5 a nonlinear system of equations with a dominant linear Performance of quad- part (e.g. heat transfer problems, inner fields of semi- rature routines conductors). Their performance is comparable to Quasi- Figure 6 Newton methods (W. Gander and L. Jaschke) Query result of the Swiss food compo- Sparse Approximate Inverse Smoothers For Geometric sition database and Algebraic Multigrid Sparse approximate inverses are considered as smoothers for geometric and algebraic multigrid methods. They are based on the SPAI-Algorithm (Grote and Huckle, 1997), which constructs a sparse approximate inverse M of a matrix A, by minimizing I-MA in the Frobenius norm. This leads to a new hierar-

chy of inherently parallel smoothers: 0, 1, and .3 Numerical examples demonstrate the usefulness of SPAI smoothers, both in a sequential and a parallel environment. Essential advantages of the SPAI-smoothers are: improved robustness, inherent parallelism, ordering independence, and possible local adaptivity (O. Bröker and M. J. Grote).

Figure 7 First three steps of a linear Krylov subspace method Computational Biochemistry and Computer Algebra

Scientific Computing Prof. Gaston H. Gonnet

http://cbrg.inf.ethz.ch/ [email protected]

Research My research activities can be grouped in 3 areas, Computer Algebra, Bioinformatics and Web-assisted teaching. In computer algebra, I am interested in the solution of equations, both in symbolic and in numerical form. Our research is closely tied with the development of the Maple system, being one of the authors of that system. More precisely we are currently working on algorithms for the the symbolic solutions of equations depending on parameters. The problem we are trying to solve is to find efficient algorithms that will analyze the special values of the parameters or special relations between the parameters which may give different families of solutions. In this area, in particular with Maple, I am still very interested in the system aspects. I.e. how to change the software, which has a substantial code and user base, to adopt modern system and programming techniques. This work is done mostly in cooperation with the company which develops Maple, Waterloo Maple, with whom we have a research agreement. This agreement has brought to ETH about 0.5M SFr in the past years. The work in Bioinformatics is centred around the developement of the Darwin system. Darwin is a language/system suitable to do computations in molecular biology. Darwin has been modelled after Maple. That is, a language which has many kernel functions which solve problems or part of problems which appear frequently in Bioinformatics. The user can use the system interactively or write his/her own functions to extend Computational Biochemistry and Computer Algebra Prof. Gaston H. Gonnet

Professor Gonnet received to the development of the For the last 12 years, his Master's and PhD Maple Algebra System. Professor Gonnet has been degrees in Computer In 1983-84, the University working at ETH, Zurich, Science from the University of Waterloo and Oxford where he is continuing of Waterloo in 1975 and University Press became work in both of the 1977, respectively. After partners for the computeri- research areas above. spending a year and half in zation of the Oxford The area of text-dominated Rio de Janeiro, Brazil, he English Dictionary. Gonnet databases has now been returned to the University was co-director of the extended to include DNA of Waterloo as professor in Centre for the New OED, sequence analysis prob- Computer Science. whose software became lems. Professor Gonnet and In 1980, together with the base for Open Text Co. Prof Benner founded Professor Keith Geddes, he In 1989, Professor Gonnet the ETH Computational formed the Symbolic was awarded the Biochemistry Research Computation Group, a Information Technology Group. The Darwin system group devoted to research Association of Canada for computational bio- in Symbolic Computation annual award for his con- chemistry has been devel- or Computer Algebra, and tributions to computer oped by this group. algebra and text searching.

the system. Darwin is a language for the specialist in searching of proteins (or their coding DNA) from the bioinformatics, mostly because of its programmability. mass of its fragments left after digestion by an Darwin is in a mature state and is used by all our stu- enzyme. This technique was first developed almost 10 dents and by many other groups around the world. We years ago to aid a community of health researchers also maintain an automatic web server, which is pow- who needed this analysis for their 2D electrophoresis ered entirely by Darwin (http://cbrg.inf.ethz.ch). Our gels. Current work is geared towards making the com- students and post-docs working in bioinformatics are putation more efficient and the selection more accu- expected to contribute their ideas not only in the form rate. of publications, but also in the form of code which can The third area of activity is related to my course in be used by the entire community. Scientific computation. This is the third course of a Currently our work in Bioinformatics is in three well series and it is geared at problem solving in Scientific defined areas: Sequence analysis and phylogenetic tree computation. With the aid of a FILEP grant from our construction, Mass profiling and system development. institution, we have developed a version of the course The work with sequence analysis touches several notes which is highly interactive, still ubiquitously areas: multiple sequence alignments, optimal estima- usable. This is possible through an architecture which tion of distance between sequences, new algorithms uses a standard browser and a central server to do any for phylogenetic tree construction and analysis of the significant computation. In this way the students, possible reasons for codon bias. Codon bias refers to besides the written material, can interact with prob- the unexplained preference of some proteins to use lems, can be quizzed and can re-work old exams. The some particular codons, which departs from the aver- web version of the notes has decreased the demand age for the organism. This latter work is done in collab- for assistancy and has increased the quality of the ser- oration with other professors in the department and vice offered. one professor in chemistry. The systems aspects of One of the main topics of the course is prediction. Darwin are quite important, as we are fully responsible The two main applications covered are the prediction for the operationability of the system. It has to be of alpha-helices in proteins (related to bioinformatics) upgraded, maintained, debugged and ported as need- and stock market prediction. For various reasons, effi- ed. Maintaining the automatic web server also con- cient algorithms for optimization closely related to sumes as significant amount of our efforts. Our goal prediction is becoming an area of interest in my with the web server is to install every significant algo- research. rithm development by our group as a service to the community. The work in Mass profiling refers to the Computer Graphics Laboratory

Scientific Computing Prof. Markus Gross

http://graphics.ethz.ch/ [email protected]

Mission Statement form various kinds of mesh processing, including filter- These days, Computer Graphics has pervaded our every- ing, enhancement, spectral estimation or edge and fea- day live. Engineers use advanced computer based mod- ture detection. Special emphasis is put on the process- eling systems to optimize the shape and geometry of ing of non-manifold geometry where advanced data their designs. Scientists visualize microstructures of structures are needed for the representation of the complex molecules invisible to the human eye and models. At data sizes that push triangle based models inspect drug proteins interactively. Medical diagnosis is to their limit, point representations are receiving grow- Figure 1 Signal processing using being strongly supported by 3-d imagery depicting the ing attention. Conceptually, points provide a discretiza- point sampled geometry interior of the human body. Advanced visual simulators tion of geometry without explicit storage of neither (St. Matthew dataset create virtual worlds of stunning realism willingly topology nor connectivity. They enable us to generate courtesy of the Digital picked up by the entertainment industry. At the turn of highly optimized multiresolution structures for the effi- Michelangelo Project, the millennium, Computer Graphics is providing cient representation, processing and rendering of Stanford University) http://graphics.ethz.ch/ enabling technology for a wide range of applications in extremely large geometry. The latest generation of algo- points/ science, engineering, art, and entertainment. Methods rithms features high performance rendering, point/pixel and systems quickly migrate from Graphics research shading, anisotropic texture mapping and advanced sig- large picture in the back: labs into the hard- and software industries and the nal processing of point clouds. high quality image gener- cycles of innovation keep shortening continuously. ation using point based Medical Simulation rendering Especially in recent years, the diffusion of affordable 3-d graphics hardware and 3-d scanning devices has been The medical simulation group designs systems for the stimulating the demand for ever more geometric detail simulation of surgical procedures with special emphasis and organic shape in graphics simulations. on facial surgery simulation. Together with our medical Contemporary personal computers place real-time visu- partners we are investigating novel techniques for 3-d al simulation and data analysis at our disposal on the reconstruction, interactive planning and prediction, as desktop. Traditionally, Computer Graphics deals both well as soft tissue modeling. One project aims at a new, with the computer based creation of geometric models more exact and more reliable way of facial surgery plan- and with the visual synthesis of real and imaginary ning. For several years we have been designing a frame- objects. Over the past decades, Graphics has matured as work for facial surgery simulation which is based on vol- a highly dynamic and rapidly evolving research field umetric finite element modeling. In various preprocess- within Computer Science. The Computer Graphics ing steps a 3-d physically-based facial model is recon- Laboratory (cgl) was founded in 1994 by Prof. Markus structed from CT and laser range scans. The theory of Gross. Its research is devoted to the design of funda- fully 3-d volumetric elasticity allows us to represent vol- mental methods and interactive systems for geometric umetric effects such as incompressibility in a natural and physics-based modeling, image acquisition and and physically accurate way. Another project deals with generation, scientific visualization, as well as virtual the exploration of advanced computational models for reality. The lab is affiliated to various international the real-time representation, deformation, and render- industrial and institutional cooperations. The current ing of soft tissue structures. The ultimate goal is to research of the cgl covers the following areas: interactively manipulate high resolution 3-d models of the human body. This includes the development of effi- Modeling and Image Generation cient representations of the underlying 3-d geometry One of our groups investigates novel paradigms for the which tolerates topological changes during surgery. representation, processing and rendering of very large A second important aspect is the fast computation of geometric objects. In spite of many surface representa- the physics of deformation balancing real-time perfor- tions devised over the decades, the triangle has widely mance and computational accuracy. survived as the major graphics primitive. We develop geometric signal processing algorithms in order to per- Computer Graphics Laboratory Prof. Markus Gross

Markus Gross is a professor His research interests of computer science and include physics-based mod- the director of the comput- eling, point based methods er graphics laboratory at and multiresolution analy- the Swiss Federal Institute sis. He has widely published of Technology (ETH) in and lectured on computer Zurich since 1994. graphics and scientific visu- He received a degree in alization and he authored electrical and computer the book “Visual engineering and a Ph.D. Computing”, Springer, 1994. in computer graphics, both He serves as a member and Figure 3 from the University of chair of international Visualization of turboma- Saarland, Germany. From programme committees chinery flow and cluster- 1990 to 1994 he was with of major graphics confer- ing in information space the Computer Graphics ences and he is associate http://graphics.ethz.ch/ Center in Darmstadt where editor of the IEEE Computer visualization/ he established and directed Graphics and Applications. the Visual Computing Group.

Scientific Visualization fundamental research in the pursuit of the develop- The scientific visualization group pursues the development of a new generation of virtual design and model- ment of fundamental methods for the display of large ing environments centering on the interaction between datasets. One project aims at improving fluid flow visu- humans and models. By integrating three-dimensional alization by automatically analyzing the data. We use human representations into immersive virtual environ- methods from computer vision to extract and classify ments, many of today’s collaboration and interaction features in flow fields. These can be employed to visual- techniques can be improved and new ones will be ize the important aspects of the flow. Extracting invented. The interdisciplinary team will build a system domain-specific features allows to reduce the amount that enables a number of participants to interact and of data to be visualized without losing important infor- collaborate in a virtual world at an unprecedented level mation. Further, the visualization not only of scientific of immersion. For this purpose, the blue-c will support data but of information as an abstract entity poses chal- fully three-dimensionally rendered human inlays, sup- lenging new problems: the underlying information porting motion and speech in real time. spaces can be multidimensional, multivariate and may lack an a priori metric defining distances and similari- Teaching Activities ties. Example applications include document retrieval, Our concept of teaching includes a sequence of courses web search, software visualization or financial data and seminars in computer graphics that allows the stu- analysis. Meaningful visualization of such spaces dents to acquire a fundamental understanding of meth- requires a far-reaching conception of information. ods and algorithms in Computer Graphics. In practical A part of our research is dedicated to the development exercises and labs, students learn how to apply Graphics of new metaphors and paradigms for information methods using contemporary APIs. At the graduate visualization. level, we offer specialized courses in advanced topics, and our graphics seminar discusses a selection of latest Collaborative Virtual Environments research results. Semester and diploma projects form a Mastering the rapidly changing computing and commu- major link to our current research projects. nication resources is an essential key to personal and professional success in a global information society. The main challenge consists not only in accessing data, but Figure 2 rather in extracting relevant information and combining Surgery simulation: Model it into new structures. The more complex and interac- and deformation field in tive tools we have at our disposal the more emphasis facial surgery simulation, has to be put on the efficient and collaborative deploy- cuts through 3-d soft tissue ment of applications. The ETH polyproject blue-c aims at http://graphics.ethz.ch/ medical/ Figure 4 Real-time multicamera acquisition system as being used within the blue-c project http://graphics.ethz.ch/ blue-c/ Laboratory for Software Technology

Computer Systems Prof. Thomas R. Gross

http://www.lst.inf.ethz.ch/ [email protected]

The Laboratory for Software Technology headed by Thomas Gross is a research group in the Computer Science Department of ETH Zürich dedicated to research in all aspects of software construction: software design and implementation, programming methodology, and performance evaluation. The principal research question that members of the laboratory address is how to reconcile compile-time and run-time resource man- denial-of-service (DOS) attacks – as a system becomes more adaptive, agement. Dealing with resource constraints (limited registers, time it will be harder and harder for a DOS attacker to identify vulnerabili- bounds, lack of memory bandwidth or network bandwidth, congestion, ties. restrictions on parallel execution, etc.) is a central problem of any effort Best-effort networks may in the future be superseded by networks that develops a realistic software system. The solutions established by that provide some QoS characteristics. However, from a software computer science research fall into two categories: methods that rely development point of view, QoS only shifts the problem of adaptation on static information (which is obtained through analysis) and meth- from run-time to compile-time: With QoS, the software developer must ods that exploit dynamic information (which is obtained during system identify what resources to ask for and then must structure the soft- execution). Use of static information enables the system to make deci- ware system in such a manner that the granted resources are never sion off-line or ahead of time (and costs associated with analysis and exceeded. So we expect that the techniques developed here will decision making are paid for only once). Dynamic methods may be able remain important for a while. to exploit information that can never be obtained statically but raise For many applications, the network provides the critical resource, new issues: What information should be gathered at run-time, and and network resource fluctuations are the prime motivation for adap- how can we ensure that the cost of information collection tation. However, for many applications, the benefits of network-based is less than the benefits that can be realized? adaptation may be lost if the operating system of the hosts is not This research question is investigated in the context of concrete included in the resource model. Real-time applications are good projects – software technology for adaptive network-aware systems examples of an application class that is solely determined by host and compiling modern object-oriented programming languages. resources. Our focus here is on "soft" real-time scenarios like the playing of a movie clip retrieved from a networked database. We anticipate Adaptive and network-aware systems that the importance of soft real-time applications will grow in the Many applications involve a network, but current best-effort networks future: standard end-systems (with generic PCs and a generic operat- make it difficult to provide predictable performance for such applica- ing system) are used in multi-media applications; the communication tions. The Remos system developed at Carnegie Mellon provides and computing capabilities of hand-held devices continue to increase, resource information for applications. Based on this system, we have but their power demands provide a new motivation for adaptivity, and explored techniques to use such information in applications. We are as more and more software for these systems is developed in an now investigating the requirements for an API that captures resource object-oriented language, the resource demands of the software are requirements for components. One area of interest is the development harder to predict (by the developer) and fluctuate during execution. of a component interface with temporal properties. Such an interface Hard real-time applications will remain important for many robotics would span the gap between the properties of low-level mobile com- or control scenarios but are outside the scope of our techniques. munication systems and applications; this project is part of the NCCR We are currently investigating how to estimate and manage the on Mobile and Self-Organizing Communication Systems. resource demands of applications; our goal is to provide the applica- Recently, we have experimented with an MPEG System filter to tion developer a tool that allows him or her to obtain realistic explore network awareness. Using the model of active services estimates of the worst-case execution time for realistic real-time Java (a refinement of active networks that pays attention to the realities of programs, and we investigate combinations of profiling and static today's networks), we investigate how to raise the availability of such analysis. a service. One technique that is promising (given the characteristics of the Internet) exploits the multitude of paths that exist between any two hosts. In the long run we expect to use such techniques to counter Laboratory for Software Technology Prof. Thomas R. Gross

Thomas R. Gross studied He joined the School a compiler) and when at the Rheinische Friedrich of Computer Science at adaptivity at runtime Wilhelms University Carnegie Mellon University, is needed. in Bonn and the Technical Pittsburgh, PA. At CMU, Professor Gross offers University Munich and he headed the development classes on software graduated with a degree of the software system for construction and an in computer science. the Warp machine and advanced course on He attended Stanford later participated in the compiler construction. University where he was design of the iWarp, a joint Thomas Gross is an adjunct part of the team that Intel/CMU project. professor at Carnegie developed the original Subsequently, he and his Mellon and is the Provost's Stanford MIPS processor; colleagues developed deputy for the NET his dissertation (advised several innovative compil- (Network for Educational by John L. Hennessy) ers (Fx, cmcc). In his current Technology). addressed how a compiler research projects, he and can help such an innovative his students investigate architecture. In 1983, what kind of resource he graduated with Ph.D. constraints can be handled in electrical engineering. statically (off-line, i.e. by

Compilers Object Race Detection Compiling modern object-oriented languages like Java that support Christoph von Praun and Thomas R. Gross threads creates many interesting questions. We are investigating Laboratory for Software Technology compilation for soft real-time environments as well as the interface Departement Informatik, ETH Zürich between the compiler and the runtime system. Our platform for exper- imentation is a Java Byte Code compiler that is targeted for the IA32 Problem and IA64 architectures. Û Unwanted ambiguity in concurrent programs through data The starting point for our investigation is the observation that for races object-oriented programs, objects are the "unit of interest" to a pro- Û Data race = unordered access to a variable, one access is write grammer. That is, the classical problem of a "data race" should be refor- Û Efficient race detection for OO program executions (Java) mulated as "object race". Then the focus of attention can be raised from storage cells to object instances, and any overhead (e.g., to moni- Approach tor accesses) can be amortized over a larger number of operations. Û Access to shared data is guarded through explicit locks Our model of object access takes into account usage patterns found Conmpliance to locking policy Û no data race in execution in many parallel programs, e.g., those that are based on the task queue Û Lockset algorithm (Dinning91, Savage97) or the producer-consumer models. Û Lockset checking at the level of objects To limit the overhead of monitoring and recording the state of objects, our approach combines compile-time methods (e.g., escape Compile- and Runtime Optimization analysis) with a code generator that produces customized code Û No checking for thread-local objects (escape annalysis) sequences. Û Deferred checking through object-ownership tracking Once objects are the focus of analysis and monitoring, many new Û Ownership lifecycle for objects: opportunities exist. E.g., a compiler with a suitable core run-time sys- first owner tem can hide many idiosynchracies of the host architecture and can (no checking) provide sequential consistency on top of a weaker memory model. As part of this project, we developed a tool to check for object races in Java programs. This tool is used to check components of the HESSI Experimental Date Center (HEDC) as well as assignments turned in by beginning computer science students.

Teaching Members of the laboratory teach a variety of classes on software construction that are offered as part of the degree program in comput- second er science and engineering at ETH Zuerich. In addition, the laboratory owner no owner (no checking) offers compact courses targeted at local professionals. (checking)

Û Exploit ILP for hiding overhead of ownership tracking

Implementation and Experience Û Way-ahead Java compiler for Intel IA-32 Û Evaluated in a data warehouse (HESSI Experimental Date Center), for several application benchmarks and in undergrad. education Û Useful detection accuracy, runtime overhead typically 20-75% Archetype of Formal Languages Raymundus Lullus’ Logical Text Machine, ca. 1275 pc

Program Languages and Runtime Systems

Computer Systems Prof. Jürg Gutknecht

http://www.cs.inf.ethz.ch/gutknecht/index.html [email protected] Majority Voting Program Constructed Systematically

Notation MA = Number of voters ( y: …) universal quantor

(Ni: …) number quantor Invariants A H = (0 ≤ s ≤ m - s) ^ ( y: y = x: (Ni: 0 ≤ i < m: f(i) = y) ≤ s) H’ = (Ni: 0 ≤ i < m: f(i) = x) ≤ m – s

Program x, m, s := any, 0, 0; { H ^ H’ } do m = M Y if f(m) = x Y skip ]f(m) = x Y if s = m – s Y s := s + 1 ]s = m – s Y x := f(m) fi fi; m := m + 1 { H ^ H’ } od { H ^ (m = M)}

Result „no one except (perhaps) x has majority of votes“

Archetype of Structured Systems Research The Sakkara Pyramid The goal of our research is the design and implementation of system models that opti- near Cairo, ca. 4000 BC mally support the development and use of current and future computer applications. Our main topics are programming languages and runtime systems, aptly illustrated by the archetypes of a logic text machine and an Egyptian pyramid respectively. Aiming at uncompromising designs and utmost transparence, we typically con- struct software systems and frameworks that directly drive commercial or custom hardware.

The Active Oberon Language The Active Oberon project is the most recent landmark on the road of integrated languages and runtimes constructed at ETHZ (see Table). The History of ETH Languages and Systems Active Oberon is a substantial evolution of the original Oberon language developed Year Language Hardware Code Type by Wirth and Gutknecht in the late 80s. Its highlights are Û simplicity, clarity and resource efficiency inherited from Pascal 1970 Pascal Apple II P interpreted Û a notion of “active” object types with autonomous behavior Û a uniform and symmetric concept of abstraction called definition 1980 Modula(-2) Lilith M micro- Û programmed a concept of block statement with associated processing attributes, including exception handling, mutual exclusion and parallelism 1990 Oberon Ceres NS 32000 native Active Oberon reflects the “new computing model”, a dynamic collection of interop- erating objects. For example, Figure 1 depicts the new computing model applied to 2000 Active SMP Intel native compilation: a set of concurrent, active parser objects, synchronizing their operations Oberon Portable StrongARM native on the shared symbol table. Definitions are Active Oberon’s sole concept of abstraction. A definition is a facet or role of an object type, including an interface specification and possibly some standard behavior. Definitions are subject to refinement and to implementation. Roughly corre- Program Languages and Runtime Systems Prof. Jürg Gutknecht

Jürg Gutknecht is an Then he studied mathe- he was appointed Assistant Associate Professor of matics at the ETH and Professor of Computer Computer Science at worked for IBM as a stu- Science at the ETH. Then, the ETH Zürich. From 1992 dent employee. In 1978 he together with Wirth, he to 1995 he was Dean of received his doctorate with developed the Oberon pro- the Computer Science a dissertation on differen- gramming language Department. In collabora- tiable function spaces. After and system. His current tion with the rector, he pio- a three year teaching prac- research interests focus on neered the US type credit tice in mathematics, he advanced programming system at the ETH.. joined Niklaus Wirth's language concepts and From 1967 to 1970 Jürg Lilith/ Modula research runtime models. Gutknecht was a member team in 1981. In 1985, after of the system program- a sabbatical stay at the ming group at Swissair. Xerox PARC Research Laboratory in California,

sponding to abstract classes, definitions subsume and generalize the notions of super- class and interface known from other object-oriented languages. For example, cargo trucks would simply be modeled in Active Oberon as objects with two facets vehicle and container (see Figure 2a), and no artificial decision in favor of one of the two asymmetric design patterns suggested by Figure 2b would have to be taken.

The Active Object Runtime Active Oberon is implemented on the Active Object Runtime, a custom made ultra- compact kernel of a mere 150 KB size that is both factory and living ground for active objects. Another novel feature of the Active Object Runtime is a carefully designed and conceptually complete API for language and compiler implementers. Currently, exem- plary implementations of Active Oberon and the Java virtual machine exist. Figure 1 The Active Object Runtime is designed to make optimal use of concurrency on SMP Language Parsers as platforms. In combination with a standardized object access protocol (for example Active Objects SOAP), it is an ideal driver for a new generation of flyweight web servers. We exploit this topic within two pilot projects, (a) a medical database of ultrasonic recordings of the heart beat and (b) a Euro project on wearable computing. In the latter project, the Active Object Runtime is predestined to drive both the “wearables” and the access points to the internet backbone.

Language Interoperability A second implementation of Active Oberon has been developed for the new .net framework in the context of Project 7, a language interoperability endeavor launched and funded by Microsoft Research. Language interoperability has become an explicit topic of our research. It is not least an important future issue from the perspective of multi-component web services. In addition to Project 7, we investigate language-independent universal semantic representations based on graph-structures.

Principles of Teaching In an instable world of fast iteration through emerging technologies, teaching is quite a challenge. Our primary concerns are separating the “essential” from the “accidential” and providing a balanced educational canon that neither neglects depth and persistence nor actuality. Our approach to a high-quality education is based on a clean separation of principles and concepts from their implementation. So have we resisted the short-sighted temptation to introduce programming with the language just en-vogue. Instead, we emphasize the systematic construction of programs based on mathematical methods. Figure 2a We use examples as the majority voting program in the Box to give an idea of the Modeling Cargo Truck quality and elegance achievable by a rigorous application of a systematic construction Objects in Active Oberon method. Further, not only do we teach the principle of separation of concerns but we Figure 2b also apply it to our curriculum. For example, we explicitly distinguish the disciplines of Standard Asymmetric programming-in-the-small and programming-in-the-large. And finally, our construc- Design Patterns for tively oriented research often directly inspires our lectures on “hot” topics, with the Cargo Truck invaluable benefit of full transparence through all system levels. Computational Sciences Figure 2 t0 4 Arrays of carbon nanotubes Computational Sciences (middle) are envisioned as a Prof. Petros Koumoutsakos technology capable of replac- ing biological sensors such as http://www.icos.ethz.ch stereocillia (top). In collaboration with nanotechnology [email protected] (at NASA's Jet Propulsion Lab) and chemistry (at NASA Ames) groups we are conducting fundamental multiscale simulations of simple and functionalised carbon nanotubes immersed in water and biomolecular environments. In the bottom figure molecular dynamics simulations of two carbon nanotubes immersed in water.

The research activities of his group are focused in the continuum simulations. We are developing particle development of computational methods and their methods, such as vortex methods, smooth particle implementation in areas such as Engineering and Life hydrodynamics and molecular dynamics, for the simula- Sciences. Computational methods include particle tion of flows in the continuum and the nanoscale level. methods (vortex methods, molecular dynamics, smooth Particle methods are robust and enjoy automatic grid particle hydrodynamics) and techniques based on bio- adaptivity. However, they are hindered by their compu- logically inspired computation (evolutionary computa- tational cost that traditionally scales with the square of tion and machine learning). Present applications include the number of computational elements. We have imple- turbulence flow control, gas turbine multi-objective mented multipole algorithms and tree data structures optimization, development of nanoscale biosensors and that reduce the computational cost, so that it is linearly modeling and simulation of biological cell processes. proportional with the number of computational elements. The efficient implementation of particle meth- Research Topics ods in parallel computer architectures is a fundamental The Computational Sciences and Engineering initiative aspect of our program. at ETH aims at actively integrating knowledge derived Applications involve : unsteady separated flows, Figure 1 from domains relevant to applied sciences (academic flows with particles, pollutant transport, nanoscale Vorticity generation and and industrial) with expertise in the fields of computer droplet evaporation and coalescence in supercritical particle entrapment in a science and mathematics. Our group is supporting this environments, flows in nanodevices and flows of bio- particle ladden flow. Particle activity by engaging in collaborative interdisciplinary logical interest such as those in small arteries and method simulations (bottom), research projects within ETH and with a number in biosensors. A new aspect of our program is the appli- have minimal numerical dissipation which enables of international institutions. cation of particle methods to the simulation of pro- them to capture the effects We participate actively in several research groups cesses associated with medical intervention. of small differences in the through ETH POLY-projects, Swiss Competence Centers initial vorticity conditions in and industrial collaborations (Alstom Technologies, etc). Nanofluidics the flow, usually only seen We are part of a strong international exchange program Nanofluidics is an enabling technology for the develop- in experiments (top). with Stanford University (Center for Turbulence ment of nanoscale devices, such as biomolecular sensors Research), California Institute of Technology (Division and actuators. Nanofluidics is the study of fluid (gas, liq- of Engineering and Applied Science) , NASA Ames uid) flow around and inside nanoscale systems. Nanoflu- (Center for Computational Astrobiology) and NASA´s Jet idics are envisioned as a key technology for designing Propulsion Lab (Microdevices Laboratory). engineering devices for biological applications, such as Our core competence may be classified in two broad biomedical devices (e.g. nanoexplorers, cell manipulators, categories, namely : particle methods and biologically etc.) in which the dominant biomolecular transport inspired computation. Applications range from the process is carried out by natural and forced convections. development of nanoscale biosensors to the optimiza- Our main subject is currently the canonical problem tion of fuel injection in industrial gas turbines. of carbon nanotubes and buckyballs and their interaction with (bio)molecular flows. We are developing Particle Methods for Multiscale Simulations the necessary computational tools for simulating bio- Particle methods are envisioned as a powerful computa- molecular flows in and around carbon nanotubes, and tional tool capable of bridging the gap of nanoscale and collaborate with experimental groups to verify the Computational Science Prof. Petros Koumoutsakos

Petros Koumoutsakos University of Michigan, Research at NASA has been full Professor Ann Arbor. Ames/Stanford University of Computational Sciences He continued his graduate and he is a member of the at ETH Zurich since studies at the California Center for Computational August 1st, 2000. Institute of Technology Astrobiology at NASA Petros Koumoutsakos, where he received Ames. From September a Greek citizen, was born a master's degree 1997 to July 2000 he had in Gythion, Laconia, Greece in Aeronautics (1988) been an assistant professor in 1963. He studied at and a PhD in Aeronautics in Computational Fluid the National Technical and Applied Mathematics Dynamics at ETH Zurich. University of Athens (1992). During 1992-1994 He is currently affiliated (1981-1986) and received he was an National Science with the Departments hisDiploma in Naval Foundation postdoctoral of Computer Science Architecture and fellow in parallel supercom- (D-INFK) and Mechanical Mechanical Engineering. puting at Caltech. Since and Process Engineering He received a master's 1994 he has been a senior (D-MAVT) at ETH. degree (1987) in Naval research associate at Architecture from the the Center for Turbulence

simulations as well as to explore novel concepts for In flow modeling we implement machine learning nanofluidic devices. Simulations of functionalised nan- techniques by suitably adjusting our approaches to the otubes and fullerenes are helping to design biosensors structure of data pertinent to unsteady turbulent flow with applications to areas such as cancer detection and fields. Due to the large scale of the problem, we are cell processes such as mitosis. encountered with computationally challenging problems such as the efficient training of neural networks with Figure 5 to 7 Biologically Inspired Computation several millions of components. The implementation of Self-organising maps are been implemented for optimization For centuries, engineers have sought inspiration from our algorithms in parallel computing architectures algorithms. The figure depicts nature in devising their creations. We are interested not enables us to overcome these difficulties and to produce the stages in the adaptation only in developing systems based on natural creations efficient learning algorithms. Their application to funda- of a self-organising map to a (biomimetics) but also in developing algorithms for mental fluid mechanics applications leads to unprece- multimodal function (left – the systematic optimization of engineering problems. dented drag reduction. Current efforts focus on the initial configuration, middle – temporary adjustment onto a We are developing optimization strategies based on evo- application of machine learning algorithms to data local minimum, right – adjust- lutionary behavior of biological systems ranging assimilation for atmospheric and environmental applica- ment to the global minimum) in scales from bacterial chemotaxis to social human tions as well as for the classification of patterns in bio- (in collaboration with IDSIA, organizations. Our goal is to develop evolutionary algo- logical cell related processes. Lugano). rithms depleted, to the extent possible, of ad-hoc heuristics, by adopting biological concepts of processes such as mutation, fitness and selection and combining them with concepts from learning theory such as self-organising maps and reinforcement learning. Of particular interest is the application of evolutionary algorithms to multiobjective optimization problems of Engineering interest. These methods are being applied on technically relevant optimization problems such as jet mixing, turbine Figure 8 to 11 blade design, and the design of micromixing devices. Evolutionary Multiobjective The robustness and portability of these approaches Optimization of an industrial enable the development of optimization tools not only gas turbine. The Pareto front in a simulated environment but also in real world (top right) corresponding to low emissions and pulsa- industrial applications. Examples include the implemen- tion is obtained for the mass tation of evolution strategies in a Pareto optimization injection parameters (bottom of a turbine design focusing on emissions reduction. right) of the fuel valves (sketch on bottom left). This Machine Learning Algorithms and Applications project is in collaboration with Alstom Power Technologies We are developing machine learning algorithms for large scale applications with a particular emphasis to application areas such as flow control and bioinformatics. In these problems scientific visualisation, statistical analysis and large scale numerical simulations are the key methods of scientific investigation, while machine learning algorithms have not been extensively implemented. Ubiquitous Computing Infrastructures

Information Systems Distributed Systems Group Prof. Friedemann Mattern

www.inf.ethz.ch/vs [email protected]

The Distributed Systems Group conducts research in models and concepts for distributed computations, distributed algorithms, Internet applications, programming of distributed systems, middleware, mobile agents, smart cards, and privacy and security concepts. Of particular interest is the emerging field of ubiquitous computing, which aims at making computers available throughout the environment, while rendering them effectively invisible. One of the main goals is to incorporate computing power into everyday objects in order to create "smart things": real-world objects that provide novel ways of accessing information, react to their environment, or provide new emergent functionality when interacting with other smart things. This vision of ubiquitous computing is grounded in the belief that microprocessors and advanced sensors will soon become so small and inexpensive that they can be embedded in almost everything. It is expected that billions of such objects will be interwoven and connected together by wireless networks, forming a world-wide distributed system several orders of magnitude larger than today's Internet. To enable communication and cooperation among smart objects, new information infrastructures are required. These infrastructures have to cope with a highly dynamic environment and should, among other things, provide location information to mobile objects, represent context information, and enable reliable and scalable service creation. The Distributed Systems Group addresses the challenges of designing and implementing such infrastructures.

Middleware Application development for distributed systems now relies more and more on software frameworks and middle- Figure 1 ware systems that provide higher-level abstractions such as distributed shared objects, and on services including MICO is a widely used secure communication, authentication, directories, and persistent storage mechanisms. Within the open source open source CORBA MICO project, our group maintains and extends a fully compliant, industrial strength implementation of the CORBA implementation. standard, which is widely used in both industry and academia. MICO also serves as our test bed for exploring novel, highly dynamic approaches to middleware, which are better suited to the size and mobility of future computing devices. We are also exploring the idea of mobile agents. By this we mean executable programs that move from a source machine to a target machine where they are being executed. Mobile agents can improve speed, flexibility, or the ability to handle disconnections, but some important problems – such as protecting agent-based applications from malicious hosts – remain to be solved. Among other things, we are investigating methods for detecting tampering with both agent code and data after it has been executed on a remote host, as well as identifying the malicious party if several hosts have been visited.

Figure 2 One of the first Smart-Its prototypes, based on an Atmel microcontroller with 128 kB of in-system pro- grammable flash memory and 4 kB of SRAM. Bluetooth modules allow communication between different devices. Ubiquitous Computing Infrastructures Prof. Friedemann Mattern

Friedemann Mattern stud- and from 1994-1999 ied computer science at the Professor of practical com- University of Bonn and puter science and distrib- became a Faculty Research uted systems at Darmstadt Assistant at the University University of Technology of Kaiserslautern in 1983. where he initiated He obtained his Ph.D. in a graduate program 1989 with a thesis on dis- "Enabling Technologies for tributed algorithms. From Electronic Commerce." Figure 3 1991-1994 he was Professor He was appointed full A typical RFID tag has the of practical computer sci- Professor at the ETH Zürich size and flexibility of an ence at Saarland University, in July 1999. address label and allows Saarbrücken, remote reading and writ- ing from up to several meters without requiring line of sight.

Smart-Its The goal of the European Smart-Its project is to develop unobtrusive, deeply interconnected smart devices that can be attached to everyday items in order to support new functionality, novel interaction patterns, and intelligent col- The Smart-Its project is one laborative behavior. Eventually, Smart-Its should be as cheap and as small as state-of-the-art radio tags (RFIDs), but of 16 projects conducted under in addition they will also be able to communicate with peers, and they will be customizable in their behavior. In the European Union's order to facilitate a meaningful integration in their environment, Smart-Its are equipped with various sensors pro- Disappearing Computer initia- viding context information. tive, whose aim is to explore The Smart-Its project is conducted in cooperation with the Perceptual Computing and Computer Vision Group how everyday life can be supported and enhanced through (ETH), TecO (Germany), PLAY (Sweden), and VTT (Finland). The research areas being addressed include: embedded the use of collections of inter- device development, perceptual computing methods for collective perception, infrastructures for smart devices, acting artifacts. architectures for context-awareness, and evaluation of application scenarios.

Security and Privacy Security and privacy will be of prime concern in a world of highly interconnected, autonomous smart devices that P3P is an open standard for will eventually permeate our everyday lives, effectively placing us under constant surveillance. This prompts the protecting user privacy on the needs for a privacy-aware infrastructure that is able to keep track of any ongoing data exchange, while providing Web, developed with the back- ing of the W3C and supported the user with a single powerful interface to selectively manage such collected personal information. Under the aus- by a large number of pices of the World Wide Web Consortium (W3C), our group participates in the creation of P3P (Platform for Privacy companies and organizations. Preferences Project), a world-wide standard for defining data collection practices in a machine-readable manner, which can then be automatically compared to the individual privacy preferences of the user. Using a trusted personal device, sensitive information can be exchanged with the environment only if the recipient matches the user's privacy preferences. An example for such trusted devices are so-called smart cards, which offer a convenient way of supplying the user with a piece of trusted hardware that is both highly mobile and ubiquitous. Within the CASTING project, our group cooperated with Swisscom to develop a security infrastructure that allows the user to utilize a mobile phone as a remote smart card reader. Any terminal that can be reached via the short distance wireless interface of the mobile phone can seamlessly use it to make applications running on these terminals more secure. In addition, we evaluate the use of next-generation smart cards, such as Javacards, in order to further simplify their usage and deployment.

Teaching Besides teaching fundamentals of distributed systems, distributed algorithms, and Internet technology, our graduate level curriculum focuses on state-of-the-art research in ubiquitous computing. Lectures are accompanied by weekly assignments and hands-on programming experience. In-depth seminars allow students to individually research and present fundamental works in the field, as well as investigate recent developments. In our ubiquitous computing laboratory, students can devise and build their own smart environments using handheld devices (e.g., mobile phones or pen-based computers), ID systems (e.g., smart cards or RFID tags), and wireless communication equipment such as Bluetooth or WLAN. Information Security and Cryptography

Theoretical Computer Science Prof. Ueli Maurer

http://www.crypto.ethz.ch/ [email protected]

allows them to compute any agreed function on their private inputs; the correctness of the result is guaranteed and the secrecy of the inputs is preserved. The project's focus is both on theoretical and on practical aspects of secure cooperations, with three main research threads: generality, efficiency, and simplicity. It was shown that more cheating can be Figure 1 Secure Cooperation tolerated in secure MPC that previously believed, the Simulation of a trusted party In a secure cooperation, a set of parties wish to cooper- complexity per operation of the best protocols was using secure multi-party ate with each other in a well-defined manner, but they reduced from n6 to n2, where n is the number of computation protocols do not trust each other. Such a cooperation could easily involved parties, and conceptually very simple protocols left figure: Specification right figure: Protocol be achieved in the presence of a party that is trusted by were developed, contrasting the highly complex proto- all other parties, but appears to be difficult when no cols known so far. such trusted party is available. An illustrative example is the so-called Modeling public-key infrastructures and digital millionaires' problem: Two millionaires want to deter- evidence mine who is richer without revealing their respective Public-key cryptography and in particular digital signa- wealth to the other millionaire. A trusted party (say a tures will play a key role in the emerging information waiter in the bar where the millionaires meet) could society. Public-key certificates establish a binding easily solve this problem, but it appears impossible to between a public key and an entity. The purpose of solve it without trusted party. Examples of real-world a public-key infrastructure (PKI) is to provide mecha- problems that can be phrased in a similar way are the nisms for issuing, storing and distributing public-key tallying process in e-voting, private access to distributed certificates and more general credentials. In absence of databases, and a solution to the software piracy prob- a globally trusted third party, this is a nontrivial issue. lem. Some concepts are not well understood in existing Such a cooperation can be realized by means of PKI standards and applications, in the cryptographic lit- secure multi-party computation (MPC) protocols, with- erature, and in legislation. Issues to be fully understood out need for a trusted party, simply by communication and practically solved are the concept of a "binding" between the parties (see Figure 1). An MPC protocol between an entity and a public key, which can have different meanings, the revocation of public keys, and link- Current Research Projects ing a digital signature to the real-world evidence of the signing entity's consent. In this project we formalize The group is active in a wide spectrum of research areas within various types of digital evidence (e.g. digital signatures, cryptography and information security: public-key certificates, time-stamps), trust assumptions Û Secure cooperation and time aspects, and develop a calculus based on Û Fault-tolerant distributed computing modal logic to describe which conclusions can be drawn Û Modeling public-key infrastructures and digital evidence from a given set of pieces of evidence. Û E-Voting Û Information-theoretic secret-key agreement Û Storage-bounded cryptography Û Cryptographic hash functions Û Indistinguishability theory Û Number-theoretic cryptography Information Security and Cryptography Prof. Ueli Maurer

Ueli Maurer gradu- tion theory, theoretical ated in electrical computer science, discrete engineering (1985) mathematics and number and received his theory. He has served Ph.D. degree in extensively as an editor Technical Sciences (1990) and a member of program from ETH Zurich. After committees, is Editor-in- spending 1990-91 as a Chief of Springer's new DIMACS research fellow book series in Information Mission Statement in the Department of Security and Cryptography, Information is becoming a crucial if not the most important resource Computer Science at and is a director of the of the economy and the society at large. Information differs radically International Association Princeton University, he from other resources; for instance, it can be copied without cost, it joined the CS Department for Cryptologic Research at ETH in 1992. His research (IACR). Maurer was the can be communicated at the speed of light, and it can be destroyed interests include all aspects 2000 Rademacher Lecturer without leaving traces. This poses new challenges for the protection of cryptography and infor- at the Department of of this new resource and of intellectual property in general. mation security as well as Mathematics, University of Information security, in particular cryptography, is an enabling tech- Pennsylvania, Philadelphia. various topics in informa- nology that is vital for the development of the information society. Our missions are Û to contribute to understanding the foundations of, and finding practical solutions for, known and emerging information security E-Voting problems, Û There are concrete plans in Switzerland and elsewhere to foresee and identify future issues in information security, Û to enable voting over the Internet. Current proposals and to advance the theory of information security and cryptogra- are based on a trusted, highly secure centralized server, phy as scientific disciplines. but one of the main problems with such a solution will be the risk of undetected manipulation or violation of the voters' anonymity. A rumor alone that manipulation has occurred can jeopardize an electronically held Zurich Symposium on Privacy and Security election. In this project we consider distributed voting This interdisciplinary symposium, founded in 1996, brings together systems with no single point of failure, and in particu- several hundred attendees each year: decision makers, privacy offi- lar we address issues like robustness and receipt-free- cers, security experts, IT-professionals, consultants, politicians, ness of voting protocols. The latter means that even a media representatives, and researchers. Some core topics for the cheating voter cannot store a transcript of the election two-day event in 2001 are new security paradigms, surveillance, and that allows him to later prove who or what he voted E-government. Privacy is becoming one of the most important issues for. As a consequence, it is impossible to sell votes, and of information society, and the symposium's goal is to identify the the massive extortion of voters becomes infeasible. most pressing issues, create awareness for them, and initiate the development of solutions. Information-theoretic security Information-theoretic security is one of the two main notions of security in modern cryptography. In contrast to computationally secure cryptosystems, which pro- Zurich Information Security Center vide security against computationally bounded In collaboration with industrial partners and research labs, in particu- adversaries, information-theoretically secure systems lar the IBM Zurich Research Lab, ETH is in the process of establishing are impossible to break even for adversaries with a research center for information security. The goal is to continue to unlimited computational power. Most of today's cryp- make Zurich a hot-bed for security research activities, attracting the tosystems are designed to provide only computation world-leading researchers to visit the center and to interact with the security, but for all these systems the security relies on center's researchers. unproven assumptions such as the assumption that factoring large integers is computationally infeasible. Figure 2 Somewhat surprisingly, information-theoretic secu- Alice and Bob share no key ini- rity is achievable if one takes into account that, in cer- tially and their goal is to share tain contexts, the laws of physics place a bound on the such a key without the adversary Eve learning any informa- amount of information an adversary can obtain. For tion about the key. The random instance, quantum physics guarantees that the mea- bit sequence broadcast by the surement of the polarisation of a photon cannot give satellite is received by Eve more than one bit of information about the polarisa- much more reliably than by tion angle. Moreover, noise in communication channels Alice and Bob. Nevertheless, Alice and Bob can communi- guarantees that an adversary receives the transmitted cate over an insecure channel bits only with some minimal (but non-zero) error prob- (e.g., the Internet), accessible to ability. This can be exploited to design cryptographic Eve, and generate a secret key systems that can never be broken, even with infinite about which Eve has essential- computing power (see Figure 2). ly no information, even if she can use unlimited computing power. Chair of Software Engineering

Prof. Bertrand Meyer

http://se.inf.ethz.ch

Figure 1 ISE Eiffel development environment (EiffelStudio)

The Challenge of software quality Component development Society's increased reliance on software systems, and In the engineering tradition of ETH, we endeavor to the astounding growth of computer hardware power, develop not just ideas but products. One of the best haven't been matched by the improvements in software practical contribution a university group can make is to development methods and tools. The work of the Chair produce public-domain reusable components with a of Software Engineering is focused on developing tech- guarantee of quality. niques for better software. We use and expand the most effective techniques Object technology available for software quality and productivity: compo- Object-oriented ("O-O") development provides a widely nent-based development, object technology with a spe- accepted conceptual basis for software development. cial emphasis on the Eiffel method and language, for- Many O-O approaches, however, make compromises mal methods and especially machine-assisted proofs, with older technologies, endangering the very benefits Design by Contract, advanced development tools. of the approach. We explore and refine the object-oriented paradigm, develop new O-O constructs, examine Trusted components the limits of the approach and its relationship with Component-based development – the construction of other directions such as functional languages. Much of software systems from prepackaged modules – is one of our work in this area is based on the Eiffel method and the most attractive avenues of progress for the software language and the ideas of Design by Contract. industry, but only if the components can be guaranteed Our work in object technology is reinforced by the to be of high quality. hosting at ETH of the Journal of Object Technology We approach the question of trusted components (JOT), set up as the leading publication in the field. through two convergent but separate roads: Û Along the "low road", we are developing a compo- Concurrent and distributed programming nent quality model designed to be broadly applicable An area of particular interest is the development of sim- and serve as industry reference. We are also developing ple, widely applicable techniques for programming con- trusted components ourselves, practicing what we current applications in their many variants: multithread- preach. ing, Internet-based systems, Web services, multi-pro- Û Along the "high road" we are exploring the applica- cessing, distributed systems, computational science tion of proof sytems to the bottom-up world of compo- applications. SCOOP (Simple Concurrent Object- nent-based development. We are also investigating the Oriented Programming) is an attempt to provide a pro- theory of proving object-oriented programs with point- gramming model that extends O-O development in a ers, dynamic allocation and garbage collection. minimal way, addressing all these variants. We are working on various implementations, taking advantage among other mechanisms of the Remoting library of the .NET framework. Chair of Software Engineering Prof. Bertrand Meyer

Bertrand Meyer's books frequently cited computer of columns in technical include Introduction to the science works in the journals including IEEE Theory of Programming Research Index list. After an Computer, Software Languages, Reusable initial career in a large Development and JOT. Software, Eiffel: the French company and at the He is a member of the Language, Object Success, University of California he board of the Académie des The .NET Training Course co-founded Interactive Technologies (Paris). His and Méthodes de Software Engineering in degrees are from École Programmation. His book Santa Barbara in 1985 and Polytechnique and ENST in Object-Oriented Software remains its scientific Paris, Stanford University Construction, second advisor. He is the editor of (MS), the Sorbonne (MA) edition won the Jolt Award Prentice Hall's Component and the University of and is among the most and Object Technology Nancy (Dr. Sc.). Series and .NET Series and

.NET and language interoperability other, as usability vs. integrity. An engineering approach Microsoft's .NET is one of the most interesting develop- requires making the proper tradeoffs consciously. ments in the area of advanced software frameworks, in particular through its support for multi-language devel- Eiffel opments. We have benefited from early exposure to Eiffel is a method and language directly supporting the .NET and the experience of a full language implementa- goals of quality software development. Fully object-ori- tion. We continue to exploit the power of .NET and ented, Eiffel provides a number of powerful techniques explore the benefits of interoperability, in particular such as information hiding, multiple inheritance, static for the construction and enhancement of reusable typing, generic classes and agents. libraries. Areas of particular interest include Web ser- Eiffel relies on the principles of Design by Contract vices, addition of Design by Contract mechanisms, and with mechanisms built into the language and directly concurrency. connected with the tools for documentation and debugging. Teaching Eiffel covers not just implementation but analysis Almost all of our work has a direct potential effect on and design as well, providing a seamless and reversible the teaching of software technology, including at an process model where developers work on the same introductory level. Our aim is not only to teach software product throughout, at various levels of abstraction, engineering the "right" way but also to capture stu- according to the Single Model Principle. dents' interest and enthusiasm through early access to This seamlessness principle implies in particular that advanced, attractive tools and libraries; and to equip graphical system views (figure 1) can be used both for students not only with immediately applicable skills but forward engineering, to generate code from diagrams as to system-building and problem-solving abilities that with a CASE tool, and for reverse engineering, to pro- will serve them throughout their careers. duce the diagrams automatically from the code, supporting a reversible, back-and-forth software process. The Journal of Object-oriented Technology The Journal of Object Technology (JOT) is available at Design by Contract http://www.jot.fm. Directed by an international The ideas of Design by Contract take their inspiration Editorial Board composed of the world's top experts in from the notion of contract, as it exists in business, to the field, JOT is published bimonthly by the Chair of provide for effective ways of designing correct and Software Engineering. Every issue includes refereed arti- robust software. Contracts bind two parties: client and cles, columns, book reviews and product reviews provid- supplier: ing a snapshot of the most current work in software Û Preconditions: conditions binding on the client, turn- development. ing into benefits for the supplier. Û Postconditions: conditions incumbent on the supplier Publications on completion of the task, turning into benefits for the At http://se.inf.ethz.ch/publications you'll find a number client. of online publications about object technology, compo- Û Invariants: general consistency conditions main- nent-based development, software education and many tained by many different operations. other software engineering topics. Contracts have five key benefits: Û Help build the software correct from the start. Software quality Û Provide documentation. Software quality is a combination of many factors, in Û Open the way to trusted components. particular: Û Help debugging and testing. Û Correctness Û Robustness Û Extendibility Û Provide managerial support. Û Reusability Û Efficiency Û Usability Û Integrity Design by Contract is built-in in the Eiffel language and Û Cost-effectiveness. supporting mechanisms have been proposed for many Some of these factors can appear to work against each other languages including C++, Java, Smalltalk and UML. Modeling and Simulation

Scientific Computing Prof. Kai Nagel

http://www.inf.ethz.ch/personal/nagel [email protected]

Our world consists of processes which evolve through time. The task of computer simulation is to provide synthetic versions of these processes. The ever-increasing power of digital computers gives us unprecedented possibilities for such simulations. Wind tunnel simulations simulate air flow around obstacles. Weather and climate simula- Figure 1 Simulation of tions allow forecasts for one day or for a hundred years. Simulations of industrial pro- Switzerland. Every pixel duction systems allow the identification of bottlenecks and the evaluation of alterna- (barely discernible) tives. Transportation simulations allow us to predict where traffic jams and pollution is an individually will move after infrastructure changes. The arguably best established methods of sim- simulated vehicle. ulation exist for partial differential equations. The concepts and methods of numerical Red pixels denote traffic jams. analysis are taught in mathematics and in computer science, and in most science and engineering classes. In contrast to this are multi-agent methods. Here, scenarios and processes are described by collections of agents or objects. For example, a transportation system is composed of travelers, vehicles, roads, intersections, traffic signals, etc. The dynamics, i.e. the time evolution of the system, is generated via rules for these objects and for their interactions. For example, a traveler may want to go from her current location to some other destination. She will enter a vehicle, that vehicle will (usually) stay on roads, it will avoid other vehicles, brake at red traffic lights, obey speed limits, etc. In contrast to partial differential equations, rules for these objects are often completely discrete. Algorithmically, this will be described by conditions, e.g. "if the traffic light is red, then brake". An advantage of this method is that it is in principle straight- forward to make the models more complex. As an important example, it is possible to make the objects/agents "intelligent" by giving them internal representations of the outside world and internal decision rules. Our group concentrates on large-scale simulations of socio-economic systems. The most mature project is the large scale simulation of transportation systems. Currently, we are working toward a 24-hour simulation of all traffic in Switzerland. Such simulation systems are composed of different modules. The currently most complex module is the so-called traffic microsimulation, where a synthetic version of the transportation infrastructure is constructed inside the computer and travelers in vehicles follow their plans. However, any such simulation also needs to generate those plans, which typically consist of activities (such as eating, working, sleeping, etc.) connected by transportation legs. That is, the interaction between how humans decide about their activities and the transportation system needs to be part of the simulation system. For example, difficult access to the downtown area may prompt people to stay at home (reduces traffic) and order pizza (increases other traffic). That is, human learning and behavior Modeling and Simulation Prof. Kai Nagel

Kai Nagel is a professor From 1995 to 1999, he was of computer science at the with the TRANSIMS (TRans- Swiss Federal Institute portation ANalysis and of Technology (ETH) SIMulation System) project in Zürich since 1999. at Los Alamos National He received a degree Laboratory in the United in meteorology/climate States, last in the position research from the of research team leader. University of Paris 6 His interests are in large in France in 1990 and scale multi-agent modeling a degree in physics from and simulation. the University of Cologne in Germany in 1991. His Ph.D. in Computer Science, obtained in 1995 at the University of Cologne, was about large scale traffic simulations.

is an important part of such a simulation package. The last part motivates another area of research: Microscopic modeling and simulation of economic behavior. We design models where economic actors follow simple behavioral rules, and study the economic outcomes. For example, simple worker-consumers produce goods which they sell to each other and then consume. We can show that simple behavioral rules lead to economically plausible economic outcomes, with the advantage that we are not bound to concepts such as rational behavior in order to describe our agents. The goal is twofold: First, investigate in how far existing macroscopic economic theory can be justified via such a "simple agent" approach as opposed to the classical all-powerful economic actor. Second, obtain well-understood building blocks in order to move to more realistic and more complex simulations later, as we have done with the transportation simulations. The clear and precise understanding of our building blocks also motivates research in the theory of traffic flow. Traffic flow simulation models, even with totally different design principles, are surprisingly robust in their behavior. This is due to the fact that the physical constraints of the system (no two cars at the same location; acceleration and braking limits) constrain the dynamics very much. There are however, differences in the way the resulting traffic changes from one regime to another, notably from the laminar to the congested regime and back. These transitions can be characterized using theory from statistical physics, where massive computer simulation is the typical tool to resolve open issues. In fact, we use this "statistical physics" approach throughout our work. The goal is not to correctly describe dynamics of single particles (such as a single traveler or a single economic actor) but the emergent macroscopic outcome when all parti- Figure 2 cles interact. It is well known from statistical physics and from statistics that this Traffic jam emergent behavior can be considerably more robust. For example, the extremely in Portland/Oregon. useful ideal gas equation can be derived from particles which do not even "see" each other. Similarly, in transportation simulations we see that we obtain plausible traffic jam behavior from very simple driving models. Thus, a general element of our method is to move to large scale simulations. Only then, with several millions of interacting particles, can we expect that statistics plays a role to make the simulation results robust. In consequence, a sizable part of our work goes into the implementation of large scale simulations. Our main platform currently are so-called Beowulf architectures, which are normal desktop Pentiums coupled via standard 100 Mbit Ethernet and using Linux as the operating system. We use these architectures because, first, our multi-agent methods map well on these architectures (as opposed to, for example, vector supercomputers), and because, second, we expect these architectures to play a major role in future modeling and simulation enterprises because of their excellent cost-performance ratio. Algorithms, Data Structures, and Applications

Theoretical Computer Science Prof. Jürg Nievergelt

http://www.jn.inf.ethz.ch/ [email protected]

Algorithms and data structures The technical focus of our research on algorithms and data structures clusters around the areas of geometry, combinatorics and search Û 1,2. We look for compute-intensive Figure 1 applications where these techniques can be brought to bear, and seek cooperation Searching for near-opti- with application experts. mal placement and mod- ulation of beams Examples of technical results are the program library ZRAM, which automatically Û in radiotherapy parallelizes search algorithms 3, and combinatorial-geometric algorithms designed to use it Û 4,5. Figure 2 Recent and current applications of geometric search algorithms include finding A toy robot programmed Û as a finite state machine. dense packings of polymers 6,7 and finding radiotherapy treatment plans that irra- diate a given target with a desired dose while damaging surrounding healthy tissue as little as possible (B. Haas, doctoral research in progress jointly with the University Hospital Bern).

Information Technology and Education The impact of information and communication technology (ICT) on education is only just beginning to be felt. The technology forces that affect the future of education are

Ph.D theses Û Ambros Marzetta: ZRAM: a library of parallel search algorithms and its use in enumeration and combinatorial optimization, 1998 Û Matthias Mueller: The structure of dense polymer systems: geometry, algorithms, software, 1999 Û Nora Sleumer: Hyperplane Arrangements: Construction, Visualization and Applications, 2000 Û Fabian Maeser: Divide and Conquer in Game Tree Search: Algorithms, Software and Case Studies, 2001 Û Currently in progress: Benjamin Haas: Automatic field setup for external beam radiotherapy. Algorithms, Data structures, and Applications Prof. Jürg Nievergelt

J. Nievergelt joined ETH His research interests have Zurich in 1975 after ten ranged widely from inter- years as a professor active systems and user of computer science at the interfaces to algorithms, University of Illinois. data structures, parallel On leave form ETH he was computation and Kenan Professor and combinatorial optimization. chairman of the Dept. J. Nievergelt is a Fellow of Computer Science at of ACM and of IEEE. the University of North Carolina at Chapel Hill from 1985 to '89.

of two kinds. First and foremost, there is a strong demand for information and com- References munication technology to become a part of general education Û 8: to be learned, in Û 1. J. Nievergelt: Exhaustive search, combinatorial appropriate dosage, by practically anybody, at all stages of the educational life line, optimization and enumeration: Exploring the poten- from elementary school to life long learning. Second, there is the use of this technolo- tial of raw computing power, 18-35 in:“Sofsem 2000 gy as a delivery tool to present information anytime, anywhere via portable interactive – Theory and Practice of Informatics“, V. Hlavac, multi-media devices, and to enhance the learning process thanks to a quality of inter- K.G. Jeffery and J. Wiedermann (eds.), Springer LNCS action unequaled by any previous educational technology. Vol 1963, 2000. The Ph.D project of Raimond Reichert addresses the design, use and evaluation of Û 2. J. Nievergelt, P.Widmayer: Spatial data struc- educational programming environments based on the simple concept of finite state tures: concepts and design choices, 725-764 in machines, such as the toy robot Kara Û 9,10. Vincent Tscherter is developing interac- J-R. Sack and J. Urrutia (eds.): ”Handbook of tive learning components that automatically generate exercises in the theory of com- Computational Geometry“, Elsevier, 1999. putation and provide step-by-step feedback. Werner Hartmann, Director of Teacher Û 3. A. Bruengger, A. Marzetta, K. Fukuda, J. Education, leads the team that created EducETH, the collection of web-based educa- Nievergelt: The parallel Search Bench ZRAM and its tional materials that is widely used in schools at various levels (www.educeth.ch). applications, Annals of Operations Research, Special issue on Parallel Optimization, Vol 90, 45-63, 1999. Û 4. J. Nievergelt, N. Deo, A. Marzetta: Memory- Information Security Consortium and Center efficient enumeration of constrained spanning trees, In the age of electronic transactions, Information Security is of vital importance to Information Processing Letters, Vol 72, No 1-2, 47-53, society, from private individuals to business and government. Together with colleagues Oct 1999. in Electrical Engineering and the IBM Zurich Research Lab, we have taken the initiative Û 5. A. Marzetta, J. Nievergelt: Enumerating the k to establish a consortium of academic and industrial institutions that share a common best plane spanning trees, Computational Geometry interest in the broad area of Information Security. A chair dedicated to creating the – Theory and Applications, Vol. 18, No. 1, 55-64, Jan Zurich Information Security Center, ZISC, is currently being advertised. 2001. Information Security is an essential component of the strategic focus "Information Û 6. M. Mueller, J. Nievergelt, S. Santos, U. W. Suter: Science" that ETHZ aims to pursue in the immediate future. Research topics include A Novel Geometric Embedding Algorithm for cryptography, applications of cryptographic protocols, operating system security, Efficiently Generating Dense Polymer Structures, access control, firewalls and intrusion detection, language-based security, hardware- accepted by Journal of Chemical Physics. based security, privacy-enhancing technology, information hiding, digital rights Û 7. S. Santos, U. Suter, M. Mueller, J. Nievergelt: management, digital payment systems, security in distributed systems, public-key A novel parallel-rotation algorithm for atomistic infrastructures, and formal methods in information security. Monte-Carlo simulation of dense polymer systems, Journal of Chemical Physics Vol 114 No 23, 9772-9779, June 2001. Û 8. J. Nievergelt: Roboter programmieren – ein Kinderspiel. Bewegt sich auch etwas in der Allgemeinbildung? Informatik Spektrum, Vol 22, No 5, 364-375, Oct 1999. Û 9. R. Reichert, J. Nievergelt, W. Hartmann: Ein spielerischer Einstieg in die Programmierung mit Kara und Java, Informatik Spektrum Vol 23 Nr 5, 309-315, Oct 2000. Û 10. W. Hartmann, J. Nievergelt, R. Reichert: Kara, finite state machines, and the case for programming as part of general education, HCC '01, IEEE Symp. on Human-Centric Computing Languages and Environments, Sep 2001. Constructing Global Information Spaces

Information Sytems Global Information Systems Group Prof. Moira Norrie

http://www.globis.ethz.ch/ [email protected]

Figure 1 OMS supported development from modeling, through design to implementation

We are rapidly moving towards an informa- OMS Database Development Suite model construction, transactional workspaces tion society in which communities of users OMS is a suite of tools and technologies de- and schema evolution mechanisms. Because will demand access to all forms of both per- signed to support the development of data- of the flexibility and portability of OMS Pro, it sonal and shared information from their base application systems from conceptual has also proved to be an excellent teaching workplaces, homes and on the move – infor- modelling through to implementation. All platform and is used in various courses at ETH mation for everyone, everywhere. Our stages are based on the same abstract model Zurich. research focuses on providing technologies of the application domain thereby ensuring Once the design is complete, it can be and methodologies to support the rapid that the application programmer’s model exported in various formats including SQL and development of global information spaces matches that of the initial conceptual design. ODMG standards for relational and object-ori- that offer access to shared information from OMS includes its own object model, inclusive ented databases, respectively. However, the various forms of client devices and employing of a full operational model, designed to be mappings involved in exporting to these plat- different modes of interaction. both semantically expressive and suited to forms result in a loss of semantic information In particular, we are exploiting object- efficient data management. and require that the application programmers oriented, XML and web technologies to We advocate that rapid prototyping be must either work with a lower-level model achieve general and flexible solutions that incorporated as early as possible in the devel- than the original application model or explic- can adapt to a constantly evolving world of opment cycle and this is supported by the itly handle the mapping between the compu- new technologies and requirements. We also database prototyping system OMS Pro. The tation and storage models. OMS Java is a data take an extreme view of databases as not OMS Pro system provides full database func- management framework designed to provide simply being repositories of application data, tionality based on the OMS model in terms of a high-level application programming inter- but rather as central system components that persistence, querying, constraints, triggers and face based on the information and storage manage user, application and system data and methods. Further, it supports the design abstractions of the OMS model. The storage control system operation. We refer to this as a process itself through graphical editors for abstraction layer provides storage platform database-centric view of system architectures. One of the major benefits of this approach is the support for dynamic system evolution.

Figure 2 OMS as the central component in a global information space with universal client access Global Information Systems Group Prof. Moira Norrie

Moira Norrie studied in Global Information Systems her home country of group in February 1996. Scotland obtaining a B.Sc. Her research interests cover in Mathematics and data modelling, object- Computational Science oriented technologies, web from the University of information systems and Dundee, an M.Sc. in information systems engi- Computer Science from neering. In June 2001, she Heriot-Watt University and took over the coordination Figure 3 a Ph.D. from the University of the ETH strategic Collection and analysis of Glasgow. Her previous programme in Information of medical data posts include lectureships Sciences. at the Universities of Edinburgh and Stockholm and a research position at the University of Glasgow. She joined ETH Zurich in 1993 and established the

independence allowing a storage platform to version of OMS Pro that enables database we developed the XD (eXtreme Design) frame- be selected based on requirements, budget components to freely connect and share both work which combines concepts of semantic and experience. A range of storage platforms data and metadata. We are now migrating the modelling and object-oriented software con- have been integrated into the framework OMS Connect concept to the OMS Java frame- struction on a meta level to enable dynamic sys- including simple persistent Java solutions, work and investigating the best way to exploit tem evolution. XD is especially tailored for relational storage engines accessed via JDBC it in the development of global information designing and implementing those parts of a and commercial object-oriented database spaces. software system managing persistent data and management systems. it was used to integrate and extend storage Paper as a Client Device? management components of the OMS Java Universal Client Access Paper++ is a European project to develop and framework. A modern data management framework must assess innovative concepts and systems that Currently we are investigating the use of support the development of applications that augment the use of paper by interleaving metamodels within OMS to represent a gen- require access from various forms of client paper documents with digital materials. As eral model of context. In cooperation with devices including desktop workstations, part of the project, we are investigating vari- researchers in product data management, we mobile phones and PDAs. The OMS Java data ous paper, printing and digital wand technolo- then want to apply this model to the repre- management framework has been extended gies to enable links to digital material to be sentation of context dependent product infor- with a general access layer to support univer- encoded within printed documents. In the mation within enterprises. sal client access through a clear separation of Paper++ project, OMS Java is being used to the notions of information, content and pre- manage both application information and the Quality in Medical Procedures? sentation to represent application entities, links between document positions and digital In the medical domain, we have developed a requested document content and document resources. Demonstrator applications are number of systems that use metadata servers presentation, respectively. The access layer is being developed based on a children’s nature to support the collection and analysis of based around an XML server and the use of encyclopedia and art gallery exhibits. patient case data for medical quality manage- XSLT for document generation from default ment. The first of these systems was a Second and customised templates. Included in the Metamodels and Metamodelling Opinion System that allowed medical practi- current set of devices supported are normal The design and use of different forms of tioners to query large sets of expert guide- telephones with a VoiceXML server providing metamodels has arisen in a number of lines for medical interventions in the fields of the necessary speech recognition and synthe- research projects within the group. One par- cardiology and gynaecology. This system was sis services. In conjunction with the Swiss ticular topic is the use of metadata servers to extended with a data collection component in Federal Institute for Snow and Avalanche support intelligent interfaces for both data support of evidence-based medicine on the Research, we are currently developing a tele- collection and querying. These servers also basis of analytical/statistical processes in phone avalanche warning service using this form the basis for the integration of various order to verify and/or qualify medical proce- framework. data sources and processing services, such as dures. After trial phases, the system is now in As part of the OMS Java access layer, we statistical packages, into information systems. full operational use in two Swiss hospitals are also developing general models and solu- This research effort has been driven by a num- where medical procedures in cardiology tions for web content management to sup- ber of application areas involving the collec- (angiography and revascularisation) are being port user customisation, context dependent tion and analysis of scientific data. These evaluated. Other pilot projects are underway rendering, multi-lingual documents and on- include systems for medical quality manage- for evaluation of hysterectomy procedures line system evolution in conjunction with uni- ment, the collection and analysis of landmine and secondary infections in hospitals. versal client access. data and regional avalanche forecasting sys- To manage the complexity and incremental tems. development of these OMS databases, it is Within the OMS Java project, we have also desirable to build these systems from compo- investigated the use of metamodels as the basis nent databases. OMS Connect is a distributed for system and application design. Specifically, Realizing the Hyperdatabase Vision

Information Systems Databases Prof. Hans-Jörg Schek

http://www.dbs.inf.ethz.ch [email protected] Transactional Coordination in Composite Systems

Database Hyperdatabase Multimedia Cluster Research Information Power DB Management

Information Figure 1 Dynamics Research areas of and Mobility the Database Group

Figure 2 Physical view on the database cluster, consisting of 128 DBMS nodes

The Vision transactions by asynchronous decentralized “coordination”. In the The amount of stored information is exploding as a consequence of following we present a short description of the four areas. the immense progress in computer and communication technology during the last decades. However tools for accessing relevant informa- Transactional Coordination in Composite Systems: tion and processing globally distributed information in a convenient We have studied the problem of ensuring correctness of concurrent manner are under-developed. In order to improve this situation, we executions in composite n-tier systems. Every coordinator in the com- envision the concept of a hyperdatabase that provides database func- posite system performs its transaction management ensuring (local) tionality at a much higher level of abstraction, i.e., at the level of com- correctness and (local) recovery. The problem is how global correctness plete information components in an n-tier architecture. In analogy to and global recovery is ensured. In the past we have extensively studied traditional database systems that manage shared data and transac- this problem from a foundational point of view, and performed several tions, a hyperdatabase manages shared information components and evaluations. In transactional processes, our more recent research activ- transactional processes. It provides “higher-order data independence” ities, we go beyond transactions in that we not only specify conflicts by guaranteeing the immunity of applications not only against between invocations but we also know about compensation and about changes in the data storage and access structures but also against retriability. We allow to specify alternative executions and based on changes in the application components and services, e.g., with respect these we generalize the “all-or nothing” atomicity of transactions to a to the location, implementation, workload, and number of replica of notion called guaranteed termination. It means that a single process components. In our vision, a hyperdatabase will be the key infrastruc- will eventually terminate along a well-defined path even in case of fail- ture for developing and managing future information systems. At the ure and under concurrency. We have started new investigations aiming interface, it will support component and service definition and deploy- at decentralized coordination exploring mobile agent technology, and ment, specification of transactional processes encompassing multiple exploiting cost information of service invocations to optimize schedul- application service invocations, service publication and subscription. ing without sacrificing correctness. Work on transactions and transac- Under the cover, it will perform metadata management, scheduling, tional processes is a foundation and a basis for transaction implemen- optimal routing of service requests, monitoring, flexible failure treat- tations in the other main research areas described below. ment, availability, and scalability. As illustrated in Figure 1, we have established a number of broad research directions tackling various Database Cluster - PowerDB problems of hyperdatabases: Transactional coordination in composite In the PowerDB project we explore a hyperdatabase consisting of a set systems continues our tradition in transaction research. The two areas of component databases in a PC cluster, which is depicted in Figure 2. below, database clusters and multimedia information management The objective is to bypass the limits of scalability and availability of benefit from transaction research and are two examples of large scale today’s database technology. In every component we have a complete information systems where we explore and realize the hyperdatabase DBMS with its data. Clients access data via the coordinator, i.e., via the vision by various prototype systems. In the vertical axis, we have hyperdatabase. We explore protocols for high-level transaction man- established a new area that complements the foundation work in agement under special consideration of semantic conflicts and of data Realizing the Hyperdatabase Vision Prof. Hans-Jörg Schek

Hans-Jörg Schek IBM Heidelberg Scientific received the Center (1972-1983, AIM pro- M.Sc. degree ject). His previous work (Dipl.-Math.) includes the developement Find Similar Insert Image in mathematics of a new method for the Images and the Ph.D. degree computation of prestressed (Dr.-Ing.) in civil engineer- cable-net roofs and its ing from University of application to the roofs Extraction of Stuttgart, Germany, in 1968 for the Munich Olympic Shape Features and 1972, respectively. Games. H.-J. Schek is a He is currently Professor of member of the VLDB Computer Science at ETH Endowment where he leads Zurich and directs the the Future Directions Observation Hyperdatabase: Process Description Database Research Group. Group. He is ACM Fellow. ETHWorld Subscription Update Before he was a professor Index INDEX of computer science at the Load Information Technical University of Monitoring Darmstadt, Germany (1983- Figure 3 1988, DASDBS project), and Term Extraction Multimedia components from Text Extraction of a project manager at the Color Features coordinated by a hyperdatabase in the ETHWorld application

partitioning and replication. Replication of complete databases con- feature vectors. In order to improve the retrieval effectiveness, we tributes to considerable speed-ups in case of read transactions. Due to support complex similarity queries consisting of several reference the second layer transaction management we avoid the disadvantages of images, several feature types, textual attributes and predicates. In traditional commit protocols and of synchronous updates. In addition, combination with relevance feedback, our similarity search system query routing aims at detecting components that have sufficiently fresh provides a convenient interface for effective queries, as exemplified data and that have the shortest response time due to queries that have in Figure 4. We further apply these techniques to organize, manage, been processed before. Replication can be full or be restricted to certain and present the individual information spaces of users in a more parts of the database. We investigate methods that dynamically allow to natural and efficient way. add more components to the cluster. We put special emphasis on “Online Analytical Processing in a Cluster of Databases”, and on “XML Document Information Dynamics and Mobility Management with PowerDB”. The combination of wireless and wired connectivity along with increasingly small and powerful mobile devices, such as laptops, Multimedia Information Management personal digital assistants, handheld PCs, and smart phones, enables Multimedia information systems consist of many specialized components a wide range of new applications that will radically change the way such as databases, object repositories, special image servers, feature information is managed and processed today. Therefore in this new extractors, and indexing components. In several projects in the past, we research area we put strong emphasis on networked information have developed a prototype system for interactive image similarity search systems where at any point in time nodes may become (partially) on a PC cluster. The cluster is coordinated by a hyperdatabase that con- disconnected. Nevertheless processing should continue with the tains descriptions of the components including their actual load. Simple objective of afterwards resolving potential conflicts if there are any, transactional processes for insertion, similarity search, and bulk load can i.e., by performing some coordination afterwards when nodes are run in parallel and the subtasks are “optimally” and reliably assigned to re-connected. In our vision, information systems will be composed the components by the hyperdatabase as shown in Figure 3. At any point of self-describing and self-organizing mobile information compo- in time, a new component can be added to the cluster in order to improve nents that are abstractions of both data and application logic. response times. Interactive similarity retrieval is based on the VA-File, a simple but efficient approximation of the inherently high-dimensional

Figure 4 Image Search: Most 5 similar images to the query image ( ) before (left) and after (right) consideration of relevance feedback. Result found in a test collection of 350000 images Perceptual Computing and Computer Vision

Scientific Computing Prof. Bernt Schiele

http://www.vision.ethz.ch/schiele [email protected]

Figure 3 (background) Figure 3 shows a user of our wearable system: a video camera mounted on the eyeglasses recognizes things the user is looking at in real-time.

Figure 1 Mission Statement The research themes of our group are consequently Figure 1 shows a screenshot Perceptual Computing in general and Computer Vision concerned with the development of methods for the of the image retrieval sys- in particular have great potentials to change the way integration of different vision models and sensor tem. The user searches for images containing 10%- we interact with computers and how machines such as modalities. A first research focus is the robust combina- 30% sky. By translating this robots perceive the world. Over the last three decades tion query to a system internal significant progress has been made in computer vision. of different visual cues and models in the context of query the precision was Today it is possible to use image information for quality object recognition and classification. As a second re- increased from 34% to 72%. control and domain specific problems such as face search focus we develop vision systems since any vision recognition, recovery of CAD models for well-defined algorithm and in particular integration should be objects and basic visual surveillance. Robustness of per- always evaluated from a complete system's perspective. ception and vision algorithms however is a notorious As a third research direction, multi sensor integration problem and one of the major bottlenecks for industrial methods are applied to the areas of ubiquitous and applications. At the same time there is little doubt that wearable computing. in the next decades small and inexpensive sensors will be developed and embedded in many devices. Our Robust Object Recognition and Categorization hypothesis is that the integration of multiple features Object recognition and categorization are among the and sensors facilitates robustness in environments of most fundamental problems in computer vision. realistic complexity. Today's approaches are unreliable, restricted to highly controlled environments or only suitable for specific Perceptual Computing and Computer Vision Prof. Bernt Schiele

Bernt Schiele is Assistant associate at the MIT Media Professor of computer sci- Laboratory, Cambridge, MA, ence at ETH Zurich and USA. His main research head of the perceptual interests are in computer computing and computer vision, perceptual comput- vision group since 1999. ing, statistical learning He received a degree in methods, wearable com- computer science from the puting, and integration of University of Karlsruhe, multi-modal sensor data. Germany as well as from He is particularly interested INPG Grenoble, France. in developing robust In 1994 he was visiting sci- perception methods that entist at CMU, Pittsburgh, work under real-world PA, USA. In 1997 he conditions. He serves as obtained his PhD from a member of major inter- INPG Grenoble, France national conferences in computer vision. in computer vision such as Between 1997 and 1999 ICCV'01, ICPR'02 and he was postdoctoral ECCV'02.

classes of objects. The combination of different object scheme can be changed and secondly the visual cues models and approaches promises to increase robustness themselves can be adapted. Two different implementa- as well as generality of today's object recognition tions of the framework show to be adequate to increase approaches. We have introduced an information theo- the reliability and robustness of tracking. retic approach for the combination of different object models on the fly and without training. This approach Next Generation of Computing has been successfully applied to face detection in diffi- Ubiquitous computing and wearable computing are cult lighting condition. among the most prominent visions for the next generation of computing. As pointed out earlier there is little Vision Systems doubt that future computing devices may have access As pointed out earlier, computer vision research should to a multitude of sensors including cameras. Such sen- be seen in the context of systems. To that end we are sors may be for example part of many small ubiquitous investigating two vision systems namely content-based devices attached to everyday objects such as personal image retrieval and visual tracking. belongings, goods in a store, or parts of a processing The majority of today's content-based image retrieval chain. systems rely on low-level image descriptors such as In the context of the European project "Smart-Its: color, texture and shape. Even though techniques such Interconnected Embedded Technology for Smart as relevance feedback have been proposed, most of the Artifacts with Collective Awareness" we develop meth- current interaction paradigms are far from the semantic ods for distributed perception and collective context- representations, which most people use to categorize awareness. The developed devices – dubbed Smart-Its – and describe image content. Therefore we have intro- can be thought of as the nerve endings duced a concept called vocabulary-supported image to a situated computing backbone serving as a platform retrieval that aims to enable the user to access an image for context-aware applications, appliances and artifacts. database in a more natural way. In this context we have The "distributed systems" group headed by developed a method to predict the system's performance Prof. Mattern is one of five partners in this project. with respect to user queries. This allows the system to The polyproject "Wearable Computing" is a joint translate user queries to internal system queries, which effort of five groups at ETH. In this project a highly con- satisfy predefined criteria such as precision and recall figurable wearable computer platform is developed. rates. Consequently, given the performance parameters Different sensors (such as cameras and microphones) of the system's sub-components, the feasibility and the are used to model and recognize the current context Figure 2 success of the retrieval process can be evaluated before- in which the wearer of the system is acting. Such con- Figure 2 contains a typical hand and optimized dynamically online. text information will be used to dynamically configure output from the visual For visual tracking we have introduced a general sys- the system. An important challenge is to achieve an tracking system: the green point clouds indicate tem framework for context-dependent multi-cue inte- optimal compromise between availability of functiona- regions with high probabili- gration as a means to obtain robust tracking in dynami- lity and the consumption of the limited resource battery ty for human heads. cally changing environments. In the literature several power. Also it is expected that context-awareness will The two ellipses are the algorithms are reported for precise object tracking in allow to implement more natural human-computer extracted head positions. real-time. However, since they are most often based on interactions. a single cue they are restricted to static or controlled environmental conditions. By combining multiple visual cues our system framework aims to increase and enable robust object tracking in dynamically changing environments. Two methodologies for the adaptation to different conditions are exploited: firstly the integration Computational Logic

Theoretical Computer Science Prof. Robert Stärk

http://www.inf.ethz.ch/personal/staerk [email protected]

Mission Statement Mathematical logic has been studied in the 20th century mainly in the context of foundations of mathematics. Nowadays, mathematical logic is playing an important role in computer science and has permeated several of its areas, including artificial intelligence, computational complexity, database systems, and programming languages. Computational logic involves the combination of computation and mathematical logic. The algorithmic aspects of computational logic include automated proof search, proof strategies, proof tactics and the development and implementation of proof assistants and theorem provers for various logics. The theoretical side of computational logic comprises the exploitation of logics for programming languages, problem specification and program verification, and the investigation of their proof-theory and semantics. Of particular interest is the development of formal methods, the core of computational logic. Since hardware and software is becoming more and more complex, formal methods have to be used to ensure security and consistency of information technology. Figure 1 LPTP – A Logic Program Verification of Logic Programs Theorem Prover One of the projects of the computational logic group is a logic program theorem prover (LPTP) implemented in Prolog. The interactive theorem prover has been designed for the formal verification of pure Prolog programs that may contain negation, if-then-else and certain built-in predicates. Properties of programs which can be proved include left- termination, equivalence of predicates, existence of solutions, unique- ness of solutions, and the equivalence of programs and specifications. The underlying logic is the inductive extension of logic programs. Unlike Clark's completion of logic programs it contains induction principles and is always consistent. The code of a Prolog predicate is translated into three positive inductive definitions of relations expressing success, finite failure and universal termination of the predicate. The main theoretical result is that the inductive extension is a sound and complete axiomatization of the operational semantics of pure Prolog with built-in predicates. On the practical side the following case studies have been successfully proved with the theorem-prover: the verification of various sorting algorithms, the correctness of a tauto- logy checker, the verification of algorithms for AVL trees, the correctness of alpha-beta pruning with respect to min-max, the correctness of a deterministic parser for ISO standard Prolog with respect to a DCG, the correctness of a fast union-find based unification algorithm. The fully formalized correctness proof of the ISO standard parser is 13000 lines long. The parser together with its specification has 635 lines. Computational Logic Prof. Robert Stärk

Robert Stärk is assistant University of Fribourg, professor of computer sci- Switzerland. In 1997 he ence at ETH Zurich since received the Fritz Winter 1999. He obtained his award. His research inter- degree in Mathematics ests are in the areas of logic from ETH Zurich in 1988 programming, formal pro- and his Ph.D. in computer gram verification, bytecode science from the University verification, deductive sys- of Berne in 1992. From tems, interactive theorem 1992-1994 he was proving, proof-theory, and Alexander von Humboldt mathematical logic. fellow at the University of Munich, from 1994-1996 visiting scholar at Stanford University and at the Figure 3 University of Pennsylvania, Definition, Verification and from 1996-1999 senior and Validation of Java research assistant at the and the Java Virtual Machine with Abstract State Machines

Verification of Abstract State Machines Java Bytecode Verification Gurevich's Abstract State Machines (ASMs) are widely used for the The book "Java and the Java Virtual Machine – Definition, Verification, specification of software, hardware and algorithms and for the seman- Validation", Springer, 2001, provides a high-level description, together tics of programming languages. When Gurevich introduced its Abstract with a mathematical and an experimental analysis, of Java and of the State Machines, he designed them to be not only a specification Java Virtual Machine (JVM), including a standard compiler of Java pro- method but also a computational model. He claimed that, with ASMs, grams to JVM code and the security critical bytecode verifier compo- one can express each algorithm at its natural level of abstraction. nent of the JVM. The description is structured into language layers and In other words, for each algorithm, one can build an ASM so that one machine components. It comes with a natural executable refinement step in the algorithm corresponds to one step on the ASM (this is the (written in AsmGofer) which can be used for testing code. The method so-called Gurevich Thesis). developed for this purpose is based on Abstract State Machines and We are developing a logic for sequential, non distributed Abstract can be applied to other virtual machines and to other programming State Machines in order to prove properties of ASMs like consistency, languages as well. The book gives the most comprehensive and con- invariants, equivalence, and sequentialization. Unlike other logics for sistent formal account of the combination of Java and the JVM. ASMs which are based on dynamic logic, our logic is based on atomic During an attempt to prove that the Java-to-JVM compiler gene- propositions for the function updates of transition rules. We do not rates code that is accepted by the Java Bytecode Verifier we found sev- assume that the transition rules of ASMs are in normal form. Instead eral examples of legal Java programs which are rejected by any com- we allow structuring concepts of ASM rules including sequential commercial or non-commercial bytecode verifier we tried. The examples position and possibly recursive submachine calls. We can show that show that Java Bytecode Verification as it has been introduced by Sun several axioms that have been proposed for reasoning about ASMs are is not possible. We propose therefore to restrict the so-called rules of derivable in our system and that the logic is complete for hierarchical definite assignment for the try-finally statement as well as for the (non-recursive) ASMs. One of the projects of the group is to build a the- labeled statement such that our example programs are no longer orem-prover based on the theoretical completeness results. allowed. Then we can prove, using the framework of Abstract State Machines, that each program from the slightly restricted Java language is accepted by the Java Bytecode Verifier. In the proof we use a new notion of bytecode type assignment without subroutine call stacks and a certifying Java-to-JVM compiler.

Figure 2 Java Bytecode Verification Parallel- and Distributed Systems Group

Computer Systems Prof. Thomas M. Stricker

http://www.cs.inf.ethz.ch/CoPs [email protected]

The trend in parallel- and distributed computing Migration of application codes to new platforms with calibrated perfor- The focus of novel computer architectures in Parallel- and Distributed mance models Computing has shifted away from unique massively parallel systems In a world of exponential growth in compute performance, some appli- competing for world records towards smaller and more cost effective cation codes and their data lives much longer than the generation of systems built from personal computer parts. The steady and exponen- computers they run on. Therefore porting applications to a new compu- tial growth of performance in commercial microprocessors mandates tational platform has become the most frequent task of software engi- the use of these off-the-shelf components in all high performance sys- neering in computational science. As the source and target platforms tems and - at this time - alternative designs do not have a real chance range from vector supercomputers over strongly connected Clusters of to compete. As predicted a few years ago, this trend leads to the over- PCs to widely distributed computers all over the Internet, some basic whelming popularity of Clusters of PCs to run traditional supercomput- characteristics of the platform change with each migration. For certain er application codes. A closer look at this trend reveals a further evolu- codes it could be advantageous to move quickly to a more cost effective tion towards even more parallelism and towards a wider distribution. platform, while for others, such would mean the loss of an efficient par- The better connectivity of most computers on the Internet will shortly allelization that offsets any benefit of the increased compute power. permit a new view of things suggesting that all those machines form a Our group provides tools and models for the characterizations of com- giant global computational grid. Therefore many application codes will putational platforms and for applications codes. It is particularly diffi- sooner or later face another migration from Clusters of PCs to this com- cult and therefore interesting to incorporate middleware into this pic- pletely distributed platform in the near future. This trend raises a few ture. We study the migration of traditional scientific codes as well as open questions regarding the suitability of the technologies involved decision support workloads running on a database management sys- and the quality of engineering that created those systems. The research tem. The platforms involved comprise vector computers, Clusters of PCs of our group is dedicated to the advancement of technology and quali- and “United Devices” (a new platform to spread a large computation all ty of engineering for Clusters of PCs and for the next generation of a over the Internet). widely distributed “grid” computing platform. Our activities fall in two categories: first, we are building systems prototypes to experiment Performance characterization of memory systems and interconnect with and to evaluate the technologies we propose, and second, we technologies reflect our experience in an improved analysis of those platforms in The most significant performance factor in modern computer systems conjunction with their applications. is the speed and the behavior of the memory system. Especially for parallel- and distributed systems, integrating high speed networks into their design, there are a large number of yet unknown interactions Intel Pentium III between the communication-system- and the memory-system-perfor- 82840 uni 3000 800 MHz mance. As a basis for the design and optimization of large parallel- and

2500 3000 distributed systems we devised a novel method to characterize memory systems and communication systems in uniform terms. The ECT 2000 2500 (extended copy transfers) memory system chart graphs the maximal 1500 2000 achievable bandwidth of a data stream within a memory system under 1000 1500 test. Data-streams with different characteristics are considered, includ- 1000 500 ing the stride of access as a parameter of spacial locality and the work-

Load bandwidth (MByte/s) L1 0 500

1 L2 ing set as a parameter of temporal locality. The ECT can be extended to Load bandwidth (MByte/s) 3 2 5 0 4 Access pattern (stride between7 64bit words) 0.5 K any networking technology that implements remote memory access. 6 2 K 8 12 8 K 16 rambus 32 K

31 Up to the present, our group collected memory system performance 15 128 K 48

24 512 K

64 2 M 32 8 M 63 data of a wide variety of machines including Cray MPP systems, DEC 127 Figure 1 96 Working set 128 Alpha Workstation Clusters and many PC Clusters based on the differ- Memory Systems DRAM Performance ent Pentium class machines. Characterization of an 800 MHz Pentium Processor Node Parallel- and Distributed Systems Group Prof. Thomas M. Stricker

Thomas Stricker University in Pittsburgh, started his Pennsylvania, USA. In his undergraduate doctoral research he inves- studies at ETH tigated hard- and software Zurich in 1982, in of high performance com- the newly founded pro- munication systems for gram for computer science parallel systems and super- & computer engineering. computers. Part of his pro- In 1988, he joined a CAD jects were done in close col- systems project at the IBM laboration with industrial T. J. Watson Research partners at Intel Laboratory in Yorktown Corporation in Beaverton, Heights, New York, followed Oregon and IBM in by doctoral studies at the Yorktown Heights. Professor School of Computer Science Stricker is a member of the at Carnegie Mellon ACM and the IEEE computer society.

Figure 2 Gigabit Ethernet - Where did all the performance go?

Linux 2.2 100 on Pentium II Speculative defragmentation - a lesson in soft- 400 MHz sophisticated incremental storage scheme to keep all previous installa- ware efficiency 80 Copy & tion images and (c) makes use of all available high performance net- Checksum Ethernet is the most successful networking work resources to replicate software images in an extremely short 60 Interrupt technology in computing. Over the past 20 amount of time. 40 TCP/IP

Percent CPU Percent years we experienced speeds ranging from 2 20 Driver/ DMA Performance issues and scalability in wireless LANs Init MBit/s up to 20 GBit/s and there were several 0 periods when the raw network speed was well Most current research in mobile computing is targeted at proposing Performance lost ahead of the speed that a single compute node new applications for wireless interconnect technologies. Design studies could handle. The most recent problem occurred with the introduction and concept prototypes are meanwhile a common sight in presenta- of Gigabit Ethernet, when more than 40% of efficiency was lost due to tions of researchers and venture capitalists alike, but those alone are unnecessary data copies and an additional 20% due to inefficient inter- not sufficient for a successful introduction of new technologies into rupt processing. Periodic shortcomings and engineering problems like widespread use. The latter requires some fundamental knowledge this raise the fundamental question of quality and efficiency in soft- about the performance characteristics and about scalability to a large ware systems. How do such software systems have to be engineered to number of users. In a joint project with the mobile computing group deliver the performance promised by the hardware? Delivering ade- we designed, installed and operate a larger wireless Ethernet installa- quate performance with specialized hardware and software could easi- tion in our computer science buildings to study performance and scala- ly be achieved, but doing so with popular hardware and with common bility of wireless LAN. software standards remains an entirely different challenge, that must be faced if relevance to practice and to the marketplace is aimed for. Up Teaching, student projects and laboratories to date it is widely believed that stable and robust system software is Building an experimental research group in applied computer science just a question of better craftsmen (or better “hackers” in a more popu- requires a significant effort and investment into a suitable research lar speak) and very little is known about the design principles that can infrastructure. Our group is maintaining a laboratory involving several improve the efficiency of code. Our group investigates the design prin- experimental computers for research and teaching activities. The facili- ciple of a speculative implementation in a highly efficient Gigabit ties include a 32 processor Cluster of PCs with different high speed Ethernet driver.This implementation technique is already widely used in interconnects, a symmetric shared memory multiprocessor, as well as a the field of computer architecture but fairly new to system software. As large number of workstations for programming and testing. On the a result the performance of Gigabit Ethernet operation in our Cluster of software front we are maintaining source code licenses for commercial PCs improved by almost 80% on the same hardware. and open source operating systems, licenses for advanced compilers and the utility software necessary to do systems research. Dolly - Operating system image maintenance by cloning While building several large clusters of PCs for classrooms and for high The CoPs (Cluster of PCs) technologies umbrella project performance distributed computing, we learned that maintaining a Most of our activities are summarized under the CoPs (Cluster of PCs) system involving a large number of software installation is a hard prob- project umbrella. The software released and the papers published can lem. Many commercial operating systems are subject to a so called be found online at http://www.cs.inf.ethz.ch/CoPs software rotting process, that leads to an inconsistent configuration state and to unpredictable failures after a longer period of service. This Linux 2.2 Standard 42 ZeroCopy Remapping deficiency requires some periodic reinstallation of the operating sys- 1 copy with Copying Driver 46 tems and the application packages (software rejuvenation). The prob- Speculative Defrag. 45 lem becomes even more critical when such systems are multifunctional with Copying Socket API 45 Figure 3 Spec. Defragmentation Performance gain and different operating systems are involved (multi boot systems). For a 65 0 copy with ZeroCopy Remapping with a novel driver better maintenance of software installations in our systems we devised Spec. Defragmentation 75 architecture based on “Dolly” - a set of tools for fast software distribution to a large number with ZeroCopy FBufs 0 1020304050607080 speculative defrag- of clients. In contrast to the utilities that are available commercially, our Transfer-rate [MByte/s] mentation system is (a) completely operating system independent, (b) uses a Distributed Computing Group

Information Systems Prof. Roger Wattenhofer

http://www.distcomp.ethz.ch [email protected] Figure 1 left A centralized system does not scale: The central processor is a security risk and may eventually become a bottleneck

Figure 2 right A decentralized peer- to-peer system scales better

Peer to Peer Computing However, file sharing is a simple form of a peer-to-peer application. A silent but major shift to distributed computing is happening. Over All major industry leaders are currently promoting their “platform for the last couple of years, Internet service providers have been connect- services; the next generation of software that connects our world of ing the world to the point where bandwidth is a lot less limited than it information, devices and people.” These Internet based distributed ser- was in the past. After a first wave of successful Internet applications, vices will need organization and coordination structures beyond con- such as electronic mail or the World Wide Web, we are currently wit- tent location. Generally speaking, all sorts of traditional data structures nessing a second wave of distributed applications, which are often such as stacks or queues will be needed in Internet style, that is, highly dubbed “peer-to-peer”. scalable, fault tolerant, and efficient. Peer-to-peer computing is the sharing of computer resources and In our group we are developing and going to deploy a peer-to-peer services by direct exchange between client systems. These resources application, presumably a game, for which we want to find a big com- and services often include the exchange of information (Napster, munity in the Internet. For this application we will implement and test Freenet, etc.), processing cycles (distributed.net, SETI@home, etc.), and our most promising data structures in order to gain real-world insights disk storage for files (OceanStore, Farsite, etc.). Peer-to-peer computing about the efficiency and availability in a large-scale system. takes advantage of existing desktop computing power and networking connectivity, allowing off-the-shelf clients to leverage their collective Decentralization power beyond the sum of their parts. The design of a highly scalable data structure is a daring algorithmic Napster is a peer-to-peer application that allows an Internet user to endeavor. We want to find data structures that are “wait-free,” that is, access content that is stored on the machines of other participating the progress of one process must not depend on the progress of oth- users. Unfortunately, the directory of the content is stored on a central ers. What is the best wait-free design for a scalable and fault tolerant server, which has become a security problem and a bottleneck with a content location service? It appears that both scalability and fault tol- growing number of participants. The location of replicated content was erance ask for a decentralized solution. determined in an ad-hoc way: Each machine that has ever accessed a Not every data structure can be decentralized. One can show that in piece of content stores it for future access; the system thus ignores the the relevant asynchronous computational model processes cannot potential lying in the optimization of access efficiency by choosing the reach a wait-free consensus without a central instance. On the other locations wisely. Despite these shortcomings, Napster has arguably hand, many data structures do not need consensus among the process- been the biggest Internet success story since the World Wide Web. es. We study the area of decentralization from a fundamental point of File sharing peer-to-peer systems such as Napster need a content view: What can be done, and how, and what can provably not be done? location service, that is, an underlying data structure that directs requests for a content to the machine where the content is stored. Ad-Hoc Networks A content location service should be decentralized; an example is the Today's wireless communication and information services are to a large Internet domain name system. A vast database replicated on many extent centralized. Conventional mobile devices require base stations servers translates URL’s into IP addresses for virtually any computer as an underlying infrastructure. In contrast, ad-hoc networking enables connected to the Internet; routing protocols such as BGP then guide wireless devices to network with each other as needed, without access the packets to their destination. to a stationary infrastructure. In an ad-hoc network the devices that Distributed Computing Group Prof. Roger Wattenhofer

Roger Wattenhofer has From 1999 to 2001 he was ad hoc networks, online been Assistant Professor of a post-doc researcher, first algorithms, randomization, Computer Science at ETH at Brown University in queuing theory, and simu- Zurich since October 2001. Providence, RI, then at lation. Roger Wattenhofer He was born in Lachen SZ, Microsoft Research in is dedicated to computer Switzerland, on November Redmond, WA. Roger science education; from 17, 1969. He received his Wattenhofer’s research 1997 to 1999 he was the computer science diploma interests include data struc- coach of the Swiss Olympic and Ph.D. degree from ETH tures and algorithms, Team in Informatics. Zurich in 1995 and 1998, distributed computing respectively. His Ph.D. thesis (e.g., routing, file systems, in theoretical computer sci- and generally scalability ence under the guidance of and decentralization of Prof. Widmayer was award- data and algorithms), peer- ed with the ETH silver to-peer computing, mobile medal. computing, networking,

are used to access the services also form the infrastructure. If a device Counting Networks p wants to transmit a message to a device q that is out of reach, there A distributed counter is a variable that is common to all are devices between p and q that forward the message in a multi-hop processes in a distributed system and that supports an manner. atomic fetch-and-increment operation, which delivers Networking without an infrastructure changes the playground dra- the global counter value to the requesting process and matically. For instance: How do we route in an ad-hoc network? Should increments it. the mobile devices establish and maintain an infrastructure for rout- Counting networks implement a decentralized dis- ing, or should they rather broadcast every message? Why should a tributed counter. A counting network consists of wires device be kind to other devices by forwarding their messages, and not (horizontal lines) and balancers (vertical dumbbells). be selfish and save precious energy? A balancer connects two wires and acts as a toggle (see figure 3): Messages arrive on the left side of the bal- New Algorithmic Paradigms ancer; the first message is forwarded on the upper wire, Traditionally an algorithm is a computational procedure that takes an the second on the lower, the third on the upper, and so input and produces an output. A large distributed system such as the on. Internet does not follow the rules of the traditional input/output para- Figure 4 shows a counting network with 4 wires. digm. We study new forms of algorithmic research, influenced by game Messages arrive on the left end of a random wire; the theory, economy, web research, and theoretical computer science. For balancers guide the messages through the network to instance: the right; the k+1st message exiting on wire w will take Û Dynamic Analysis: A large distributed system such as the Internet is the value 4k+w. dynamically changing. Machines and connections come and go. How Counting networks come in all sizes. Background fig- can we maintain global data structures that tolerate these changes? ure 5 shows a counting network with 16 wires, where Û Locality Gap: Due to the inherent dynamics of large systems it is each message has to traverse 10 balancers. often impossible to give globally optimal solutions. Local optimizations might be a feasible way to go. How much efficacy and efficiency is lost because of this? Û Online Algorithms and their analysis capture the lack of performance due to uncertainty about the future. For example, we need to decide how to route a stream of packets without knowledge of future routing requests. Û Selfish Agents: In some large distributed systems such as the Internet not all entities cooperate. Algorithms for selfish agents study how to design a protocol for agents that follow their own interests and tune the parameters of the protocol for their own benefit. What hap- pens for instance if a selfish Internet user increases her TCP window size to get more throughput? Û Malicious Agents: It is a small step from being selfish to being malicious. What can we do when entities in a distributed system malicious- ly sabotage the system? How do we deal with malicious agents? How many malicious agents can we tolerate and still guarantee correctness and efficiency of the system?

Figure 3 top Figure 4 bottom Figure 5 background Theory of Combinatorial Algorithms

304140932017133780436126081660647688443776415689605120000000000 Figure 2 A path from bottom Theoretical Computer Science to top in a 3-dimensional Prof. Emo Welzl polytope – not the shortest one, obviously http://www.inf.ethz.ch/personal/emo [email protected]

Even computers a million times faster than current paths on d-dimensional polytopes are completely unre- technology will not be much of a help, if a solution to a solved. problem takes 1050 steps; not even, if a million of such We have contributed to the currently best runtime computers are at disposal to work in parallel. bound known for the simplex method for LP and LP- Algorithms theory seeks for methods that significantly related problems like computing the smallest ball reduce the number of steps that are necessary to solve enclosing a set of points in d-space. For linear (and more a problem (independently from the current state of general mathematical) programs that are at the heart hardware technology), or it demonstrates the inherent of many geometric optimization problems, combinato- Figure 1 49! difficulty (complexity) of solving such a problem. The so- rial methods provide the state-of-the-art solutions. 2 the number called combinatorial explosion is omnipresent in many We have developed and implemented some of them. of tours through 50 situations: For example there are more than 10 tours 50 cities through 50 cities, so if you let a program go through all Sample Based Modeling these possibilities in order to find the shortest tour, your Recent advances in scanning technology and a number life span, and most likely that of mankind, will not of reconstruction algorithms have opened a new para- suffice to produce the solution. Still, current methods digm for modeling shapes from samples. Usually sam- can quickly find such an optimal tour through 50 and ples are given as unstructured point sets. The simplest many more cities. The development of such methods case is where the sample is taken from a curve. goes hand in hand with a better understanding of the The most important case from a practical point of view underlying mathematical structure of the problems. is where the sample is taken from a surface in 3-space. It comes as little surprise, that theoretical computer sci- We have contributed to the understanding of both the ence finds itself located at the borderline between reconstruction of curves as well as surfaces. The goal mathematics and computer science. is to develop methods that guarantee a good recon- It is our goal to contribute to this development of struction under certain conditions. We are still partici- combinatorial algorithms and of algorithmic paradigms, pating in the search for such methods that are both and to support the transition of results to applications. efficient and provably good, and that can handle the We are primarily interested in geometric problems, opti- challenges of undersampling, noise and large data. We mization and in the employment of randomized meth- also broadened our research to include topics like sam- ods that play a crucial role in theoretical computer sci- ple decimation and feature detection from samples. The ence. The following presentation cannot provide more main tools we consider useful are Voronoi diagrams and than a number of snapshots reflecting our activities. Delaunay triangulations, whose algorithmic treatment has been well developed in computational geometry. Combinatorial Aspects of Optimization Many problems in Operations Research can be formulat- Computational Geometry Algorithms Library ed as a linear program, or a linear program appears in One major drawback of sophisticated algorithms is that an intermediate step towards the solution. The most they are sometimes hard to understand, and many prominent methods for solving such problems are the 'hidden' details make them hard to implement. So often simplex algorithm (a combinatorial method), and inte- the user will fall back on an inferior method, simply rior point methods. We are interested in combinatorial because the threshold of implementing a better algo- methods. For example, the simplex algorithm with its rithms is or appears to be too high. The problems get various pivot rules peforms well for most instances amplified for geometric algorithms (as compared to in practice, but its theoretical behaviour is by no means purely combinatorial ones) by the numerical problems to understood. In particular, very basic questions about which sophisticated methods are particularly sensitive. Theory of Combinatorial Algorithms Prof. Emo Welzl

Emo Welzl has been profes- optimization, randomized University, Humboldt sor of computer science at methods, analysis of University, University the Institute of Theoretical geometric structures and of Technology, and the Computer Science of ETH discrete geometry. Konrad Zuse Center Zurich since April 1996. He received a degree in in Berlin from 1991 He is co-chair of the Berlin- Applied Mathematics at until 1996. Zurich graduate program the Graz University of In 1992 he received the on "Combinatorics, Geo- Technology, Austria, and Max Planck Prize with metry, and Computation." a Ph.D. under the super- Micha Sharir from Tel Aviv His research interests are vision of Hermann Maurer University, in 1995 the in the foundations of with a topic in formal Gottfried Wilhelm Leibniz computer science, mainly languages in 1983, also Prize. He is ACM Fellow algorithms and data in Graz. 1987-1996 he spent since 1998. structures, in particular as a professor of computational geometry mathematics at Free and applications, University of Berlin. combinatorial aspects of He served as chair of the graduate program "Computational Discrete Mathematics" at Free

In an effort to overcome this hurdle, an initiative of several European universities is providing a computational geometry algorithms library, called CGAL, in which ETH is participating. Apart from the issues of efficiency, handling degeneracies (special cases) and numerical problems, one of the major challenges is to allow sufficient genericity i.e. to supply an interface that easily and efficiently adapts to several data formats.

Discrete Geometry The analysis of extremal, average or 'typical' geometric configurations is closely related to the performance Figure 3 to 5 analysis of algorithms. And the understanding of the An unstructured sample, a structure of geometric configurations is important for curve reconstruction and a the understanding of geometric algorithms. surface reconstruction For example, the probabilistic method has been used for long in mathematics in a non-algorithmic context, before it became one of the most powerful paradigms in computing. But sometimes, the inspiration goes the other way round, and the algorithmic tools, or simply an algorithmic way of thinking leads to progress on a purely mathematical problem. Many simply stated geometric problems are still far from being solved: E.g. one of the famous Erdos problems asks, how often the same distance can occur in a set of n points in the plane. For the related problem of Erdos', the minimum number of distinct distances of n points in the plane we supplied a significant improve- ment recently. Two of the classics in discrete geometrie are the so- called Upper Bound Theorem and the g-Theorem. They provide useful constraints on how the combinatorial structure of a convex polytope in d-space can look like. We have recently established a number of surprising connections of these theorems to other problems of low dimension (where the original statement is needed for arbitrary d); notably a connection to problems in sto- chastic geometry. Algorithms, Data Structures, and Applications

Theoretical Computer Science Prof. Peter Widmayer

http://www.ti.inf.ethz.ch/pw [email protected]

Figure 1 3-dimensional view of the area around Luzern. The combination of digital elevation models (DEMs) with orthophotos produces a realistic view of the terrain. DEM and orthophotos ©Endoxon AG.

Research: Our Approach tion that is useful to a practitioner provides the final As computers become more and more powerful and proof of concept and makes the research and develop- omnipresent, they are expected to solve increasingly ment result accessible. This needs an interaction para- difficult problems. However, this is possible only with digm that makes the software intuitive to use – and it sophisticated algorithmic machinery. We develop data may therefore impose extra algorithmic requirements. structures and algorithms for combinatorial and geo- It is this feedback between the stages that motivates Figure 2 metric problems from a variety of application areas. us to span the entire development process for data Zurich double- Our basic algorithmic experience is helpful in all of the structures and algorithms for applications. decker suburban problems, but their broad variety helps us gain key railway insights into underlying principles, difficult to discern Research: Some Current Projects Figure 3 from a single application. That said, our focus is on prob- Project: Spatial Data Structures and Algorithms Intercity com- lems involving large data sets and hard optimization Mobile phone antennas have spread, and new antennas muter train in questions. The problem areas we consider include still need to be added as the technology changes and Ticino spatial data structures and algorithms, optimization becomes even more popular. In the interest of the gen- Figure 4 problems in railway networks, distributed data and eral population, this spread should be controlled accord- "Roter Pfeil" structures, data structures and algorithms for computa- ing to laws and regulations, and even beyond that RAe2/4, tional biology problems, communication network by coordinating across mobile phone providers. On the background: Castle Grandson optimization algorithms, approximation algorithms for other hand, a certain spread is desirable, so as to enable packing and covering problems, and other discrete mobile phone calls as needed. We study the theoretical Figures 2 to 4: optimization problems. complexity of optimum mobile phone antenna place- © Foto-Service SBB Our work spans a wide spectrum, not only in the ment on a terrain. In general, even simple problem ver- problems studied, but also in the algorithm develop- sions are hard to solve optimally, or even approximately. ment process. We distinguish four stages in algorithm This is true for a large family of geometric problems development for applications. First, the study of real dealing with covering and packing. Hence, we develop world issues leads to an abstract version of the given heuristic solutions and study their qualities. These solu- problem. Second, theoretical data structure and tions are a basis for very general optimizations, includ- algorithm design yields a solution with performance ing the location of antennas, their characteristics, and analysis, as well as insight into theoretical limitations. the assignment of frequencies. Furthermore, they allow The closer the abstract problem models reality, the the interactive progressive optimization, taking user more useful is the theoretical result. On the other hand, feedback into account as the optimization proceeds. a more abstract problem that is less realistic for the Our prototype software system is in use for optimizing given application can add more to our fundamental several networks of antennas in Europe, and we contin- knowledge. Third, an experimental implementation ue to develop it to take more objectives into account. and a study with application data complements the For this system to be useful, we developed and theoretical analysis – and leads to reconsideration of implemented a virtual reality type interface. The user stages one and two. Fourth, a prototype implementa- can virtually fly over the terrain and explore antenna Data Strucures, Algorithms, and Applications Prof. Peter Widmayer

Peter Widmayer got a Ph.D. in graphs. He was a full in industrial engineering professor of Computer at Karlsruhe University Science at Freiburg in 1983, with a thesis on University from 1988 computational complexity to 1992, and he has been in computer graphics and at ETH Zurich since. VLSI design. He spent a year His research interests as a postdoc at the are in data structures, IBM T.J. Watson research algorithms, and center and returned implementations to Karlsruhe, where for combinatorial and he received his Habilitation geometric problems. in 1986 with a thesis on Steiner´s problem

positions, radiation patterns, and any other information Project: Distributed Data and Structures selected from a database. The interactive visualization People want to access data from anywhere, regardless is loosely attached to the database of terrain and tex- of small failures of the involved computers and links. ture data, antenna data, and other data. Efficient access Furthermore, access to large data sets may be faster is crucial for the real-time flight: terrain data and tex- if the data are spread across a large set of server nodes ture data can be accessed according to location and in a distributed network, to avoid the bottleneck in- loaded with an increasing degree of detail, by means of herent in a single machine servicing many requests. a spatial index for weighted objects. We use the data- Our theoretical studies are concerned with how data base system blocking and addressing facilities to impose should be thus distributed, and how they should be the index onto the physical storage structure. Specific indexed so as to allow efficient access in spite of both algorithms for multiresolution triangulation and for node and edge failures. The results vary with the details hierarchical compression of pictures complement the of the model; our interest is in identifying the crucial access structure. properties of the model that permit an efficient solution, and in developing such a solution. Eventually, we Project: Railway Optimization aim at distributed implementations of various data The mobility of people results in the need for efficient structures for large data sets. Figure 5 public transportation. As roads become more and more Wave propagation congested, railways enjoy great popularity, and they Teaching prediction of two even approach their physical limits at peak hours. Apart from the elementary and advanced courses and directional GSM antennas. We study optimization questions for railway transport seminars we cover in algorithms, we also take part in The simulated field in a European context. In particular, we investigate the the joint Berlin-Zurich graduate program on Combina- strength decreases problem of realizing a given schedule with a smallest torics, Geometry and Computation. In an attempt to from dark red number of train components. This study also aims at understand the implications of information technology to light yellow. creating schedules that satisfy a given demand in a best on education, we teach with a multimedia system DEM and ortho- possible way, with objectives such as little congestion (authoring on the fly), we record lectures and make photos due to service trains, and robust connections. In general, them available on the web, and we develop tools ©Endoxon AG. this problem is theoretically tractable only if the most to support this form of lecturing. basic constraints (such as regular maintenance requirements) are ignored. However, real trains may not corre- spond to hard problem instances. We explore the relation between theoretical hardness and practical feasibility. It turns out that for real trains, our experimental software leads to a surprising savings. In cooperation with railway companies, we are developing algorithms for a variety of objectives under a large number of possible constraints. Even in a robust schedule, a connection can be missed due to unforeseeable events. Humans can easily correct for small disturbances, but the same response is difficult to derive automatically. Even for simple settings and limited reactions, the problem is hard to solve in general. We study the practical situations that arise, and we work towards an automatic reaction that is intuitive and can be found instantly. Development and Application Group

Information Systems Prof. Carl August Zehnder

http://www-ea.inf.ethz.ch/zehnder/index [email protected]

Benutzer Dozentin Lehrveranstaltung

Modulentwickler ETH WebQuality

Feedback-Server http://webquality.ethz.ch/feedback/server/

The Development and Application Group works on selected topics in the broad and still growing field of "practical Information Technology" with two major goals: Û Auswertung Auswertung to integrate and improve academic methods and nonreaktiver reaktiver standards into and for daily-life IT applications, and Erhebungen Erhebungen Û to transfer the knowledge about those methods to university students (through lectures and seminars as well as student projects). Those selected topics include currently: ICT infrastructures for schools: Schools have specific needs concerning effective and efficient maintenance and support of ICT infrastructure. Which concepts and experiences from business and industry can be trans- ferred to school environments? Which solutions have to be developped especially for schools? For schools long range aspects must prevail. The results of our studies are published to help teachers, support staff and school authorities directly. Development and Application Group Prof. Carl August Zehnder

Carl August Zehnder (born of databases and project 1937) graduated in Applied management. Beside these Mathematics at ETH Zurich academic activities he (Dr. sc. math. 1965), served in many manage- programming as early as ment positions in his uni- 1958. After a postdoc year versity (incl. ETH at MIT in USA he returned Vicepresident 1987 – 1990) to ETH, first in Operations and in major Swiss profes- Research, then switching sional associations; he is to Computer Science publisher of the Swiss (Ass.Prof. 1970, ao. Prof. Revue INFORMATIK/ INFOR- 1973, full Prof. 1979), where MATIQUE. he built up the fields

E-Government Interface: Government information sys- Teaching tems should be able to cope with heterogeneous net- The Development and Application Group is responsible worked environments including volunteer citizens. IT pro- for the introduction of all Computer Science students to jects in this field can no longer be isolated in a single IT Project Management (in 5th semester); this course government agency. Even autonomous public bodies opens the view toward IT projects in industry as well as must cooperate to achieve efficiency and to make the to student project work as part of the curriculum. An interfaces between public administration and citizens as other – and substantially growing – area of teaching cov- lean as possible. ers "IT for Engineers" where general IT concepts and in a Information Management: Enterprise information sys- second course databases and information systems are tems should be based on a coherent view of information presented to non-IT-specialists (mostly graduate students needs, made visible through high level information con- in production and electrical engineering) with a specific cepts. The CUBORO method supports the building of such view to applications. For IT engineers are the upper level concepts. courses "Building large information systems" and The Swiss IT Workforce: In cooperation with federal "Information Management". agencies and with the major Swiss professional IT Beside those courses the Group is heavily involved in associations a database and a Web-based information seminars and experimental forms of teaching, especially platform ("IT Switzerland", www.i-s.ch) is built up to im- also to promote group work and interdisciplinary think- prove education planning for IT professionals. ing. Good examples for this are the seminar "Computer and Law", held together with law and IT professors of the University of Zurich regularly since 1973, and the course "Problem solving in daily IT life“. Contacts and Addresses

Head of Department Prof. Peter Widmayer [email protected]

Head of Administration Peter Koschitz [email protected]

Mailing address of the Department Department of Computer Science ETH Zentrum CH-8092 Zurich Switzerland

Phone numbers Department Administration +41-1-632 72 01 Student Administration +41-1-632 72 11 Continuing Education +41-1-632 72 06

Fax number +41-1-632 16 20

World-Wide Web http://www.inf.ethz.ch

For general information [email protected]

Impressum Design kursiv, Katrin Schek, Berlin [email protected]

Redaktion Peter Häni, Zurich

Bilder Lisa von Boehmer, Zurich

Department of Computer Science ETH Zentrum CH-8092 Zurich Phone +41-1-632 72 01 Telefax +41-1-632 16 20 http://www.inf.ethz.ch E-mail [email protected]