The Network as a Global Database: Challenges of Interoperability, Proactivity, Interactiveness, Legacy Peter C. Lockemann, Ulrike Kijlsch, Arne Koschel, Ralf Kramer, Ralf Nikolai, Mechtild Wallrath, Hans-Dirk Walter {lockemannJkoelsch~koschel~kramer~nikolai~wallrath}~fzi.de Fakultat fur Informatik Forschungszentrum Informatik (FZI) Universitat Karlsruhe Haid-und-Neu-Str. lo-14 D-76128 Karlsruhe, Germany D-76131 Karlsruhe, Germany 1 Introduction Abstract Modern information and communication technology is The current integrated developments in net- the driving force behind the future highly intercon- work and computing give rise to a technical in- nected society. This raises high challenges to those frastructure for the information society which that are entrusted with t.he technical infrastructure for one may variously circumscribe by terms such society, and it places high responsibilities on them. To as ubiquitous computing, telepresence and the meet these, one should start from a global view on network as one giant global database. The pa- this infrastructure. To develop a consensus on such per applies to the network the metaphor of views the use of metaphors is commonplace. For the global database, and subsumes the aspects of networked infrastructure three metaphors are usually ubiquity and telepresence under it. It should mentioned, each corresponding to a different angle on then be possible to preserve many of the ex- it. One is ubiquitous computing which refers to the isting database techniques and to concentrate utilization of computing power of whatever kind when- on adjusting these to the network information ever and wherever the need arises. Another is telepres- infrastructure. ence (or in the extreme, omnipresence) - the ability to The paper explores four challenges for ad- be present anyplace without physically moving there, justment: interoperability due to heteroge- and to be at several places simultaneously. Telepres- neous data repositories, proactivity due to ence is based on telecommunications that is no longer autonomy of data sources, interactiveness due point-to-point and person-to-person, but may involve to the need of short-term and task-specific person-to-group or group-to-group relationships which interaction and cooperation, and legacy due open up many new avenues of creative collaboration to the fitting of old systems to the net- and problem-solving. A third angle is the view of the worked environment. Based on several appli- network as one giant global database indicating that cation projects and exemplary solutions, the information becomes a shared commodity with equal paper claims as its experiences that object- access by many or all, instant reading and posting of orientation provides a natural framework for items from anywhere by anyone. meeting the challenges, but must also draw All three angles appear equally proper and, hence, on the combined resources of databases, data seem to indicate that only an interdisciplinary ap- communications, and software engineering. proach will ultimately be able to meet the challenges of Permission to copy without fee all or part of this material is the network information infrastructure. On the other granted provided that the copies are not made OP distributed for hand, in any given situation one will have to emphasize direct commercial advantage, the VLDB copyright notice and one of them which will then determine the predomi- the title of the publication and its date appear, and notice is nant technology under which one plans to strike out given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, or to republish, requires a fee at the technical and organizational problems for the and/or special permission from the Endowment. network. Proceedings of the 23rd VLDB Conference This paper chooses the metaphor of global database Athens, Greece, 1997 as its primary perspective. For one, this seems a natu- 567 ral choice because databases pervade the entire fabric which originated from distributed Artificial Intelli- of an organization, as they do in industry, commerce, gence but has another more technical root in telecom- and public administration. For another, it seems a munications. Agents are software components that technically sound choice because databases can be con- seem to assume a life of their own, respond to requests sidered a mature and reliable technology, though not in some autonomous fashion that includes decision- necssarily in a network of thousands of loosely cou- making capabilities, become proactive by initiating ac- pled, heterogeneous nodes. The purpose of the paper tions seemingly without outside intervention, adapt is to explore, on the basis of a number of case studies to their environment by exhibiting learning capabil- for practical applications, whether the choice is indeed ities, enter into contracts with one another if there is a a productive and constructive one, and if so, what ad- need to interact, and may even move through the net- justments are needed to the traditional database tech- work to where the action is [CCWB94, Pog95, WJ95]. niques, with which well-understood techniques from All these are properties that we must expect from other disciplines they should be amalgamated and how the nodes in the network. There are indications that this is to be done. objects are a promising implementation concept for Such an exploration requires a framework on which agents [BGK+95, GKT95]. In particular, if one en- all the disciplines involved can agree. We claim that capsulates within each object its own process one ob- object-orientation is such a framework (Section 2). We tains a basis for the desired autonomous, proactive then examine a number of challenges to database and and interactive capabilities. Hence, whereas in the tra- other technologies. One has to do with the technical, ditional approaches to object orientation objects and semantic and pragmatic heterogeneity of data reposi- processes are treated as orthogonal notions, the two tories which must be overcome by suitable means for become tightly interconnected in a networked world. interoperability (Section 3). Another has to do with Since independent processes may run concurrently, co- the autonomy of data sources which suggests that operation between objects in a network implies coop- databases no longer just respond when a particular eration among processes. service is requested from them but become active on In summary, object-orientation seems a particularly their own, requesting services from other network com- useful technical framework for the network infrastruc- ponents. The paper illustrates how proactivity can be ture for modern society. At the same time, since added to a system of distributed databases (Section object-orientation is also a concept underlying many 4). A third challenge is how to exploit the potential modern developments in datatabases, particularly in for collaborative behavior by providing the means for the form of object-oriented database systems, it pro- concerted action of database nodes in order to solve vides a suitable foundation for the view of the network common tasks (Section 5). Section 6 addresses the as a global database. challenge of how to preserve earlier investments and nonetheless fit legacy systems to the networked envi- 3 Interoperability ronment . Interoperability refers to the capability of indepen- 2 Object orientation dently developed objects to productively interact across a network of heterogeneous platforms and ser- Object-orientation is a technical framework that gives vices. Interoperability has three aspects: cohesion to a wide range of information technological disciplines and, hence, appears as an ideal framework l Platform interoperability overcomes the hetero- to meet the interdisciplinary challenges of the infras- geneity of the hardware and system software in tructure for the networked society. The reasons are the nodes of the network, and of the services that manifold. Objects allow any measure of compartmen- transport messages between the nodes. talization and, together with encapsulation, the con- centration of functionality along a service-oriented ra- l Notational interoperability surmounts disagree- tionale and of information along a need-to-know prin- ments among the objects (application programs, ciple. Objects interact by exchanging messages. Ob- tools, databases) on the structure, representation jects may adapt their responsiveness without chang- or interpretation of the data (denotation) they ing their interface to the surrounding world. Objects wish to exchange, which often reflect differences may be replaced by “better” objects without disturb- in universes of discourse, perceptions, attitudes, ing their surroundings as long as their interface re- and goals (connotation). Typical effects are dif- mains the same. ferent or even incompatible functional interfaces, A more recent rationale for object-orientation is its data models, data types, database schemas, ter- closeness to the technical metaphor of society of agents minologies, and data formats. 568 I I Information Services Data Services Figure 1: Architecture of a CORBA-integrated federated information system l Coordinational interoperability imposes discipline database. Consequently, the user interface should be on the interaction between objects, and is usually uniform and hide all aspects of distribution. expressed by common policies, contracts and pro- Figure 1 depicts a high-level view of the system