l II t OFPY Massachusetts Institute of Technology Laboratory for Computer Science July 1984- Progress Report June 1985 22 00 N N N N DTIC ELECTE SEP2 7 199011 DISTRIBUTION STATEMENT A Apprmo,?d 'or public release; Dist budon Unbrrits-d Unclassified SECURITY CLASSIFICATION OF THIS PAGE REPORT DOCUMENTATION PAGE Ia. REPORT SECURITY CLASSIFICATION lb. RESTRICTIVE MARKINGS Unclassified 2a. SECURITY CLASSIFICATION AUTHORITY 3. DISTRIBUTION /AVAILABILITY OF REPORT Approved for public release; distribution 2b. DECLASSIFICATIONIDOWNGRADING SCHEDULE is unlimited. 4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S) MIT/LCS/PR-22 6a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION MIT Lab for Computer Science (ifapplicable) Office of Naval Research/Dept. of Navy 6c. ADDRESS (Cty, State, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code) 545 Technology Square Information Systems Program Cambridge, MA 02139 Arlington, VA 22217 Ba. NAME OF FUNDING I SPONSORING 8b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (If applicable) DARPA/DOD I Sc. ADDRESS (City, State, and ZIP Code) 10. SOURCE OF FUNDING NUMBERS PROGRAM PROJECT TASK WORK UNIT 1400 Wilson Blvd. ELEMENT NO. NO. NO. ACCESSION NO. Arlington, VA 22217 11. TITLE (Include Security Classfication) MIT Laboratory for Computer Science Progress Report - 22 12. PERSONAL AUTHOR(S) Dertouzos, M.L. 13a. TYPE OF REPORT 113b. TIME COVERED 14. DATE OF REPORT (Year, Month, Day) IS. PAGE COUNT Technical /Proqress FROM 7/84 TO 6/_8_5 June 1985 266 16. SUPPLEMENTARY NOTATION 17. COSATI CODES 18. SUBJECT TERMS (Continue on revere if necesary and identify by block number) FIELD GROUP SUB-GROUP Computer Architecture, Computer Science, Computer Systems, Electrical Engineering, Networks.Theory of Computers, Programming Languages 19. ABSTRACT (Continue on reverse if necessary and identify by block number) Annual Report of Progress made at the MIT Laboratory for Computer Science Under Contracts: a.) N00014-83k - 0125, Darpa Order 5602/2095 b.) N00014-84k - 0099, Darpa Order 4920 20. DISTRIBUTION/AVAILABILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION (3 UNCLASSIFIEDIUNLIMITED 0 SAME AS RPT. Q DTIC USERS Unclassified NAME OF RESPONSIBLE INDIVIDUAL 22b. TELEPHONE (Include Area Code) 22c. OFFICE SYMBOL Carol Nicolora (617) 253-5894 DO FORM 1473, 84 MAR 83 APR edition may be used until exhausted. SECURITY CLASSIFICAT ON OF THIS PAGE All other editions are obsolete Unc lOaifedAM" Offin US-w44 Unclassified Massachusetts Institute of Technology Laboratory for Computer Science July 1984- Progress Report June 1985 22 Accession For ,.'IS GRA&I DIlUC TAB Una~nnounced El Justificatio By, Distribution/ Availability Codes Avail and/or Dist Special I nnI I UU I uu The work reported herein was carried out within the Laboratory for Computer Science, an MIT interdepartmental laboratory. During 1984-85 the principal financial support of the Laboratory has come from the Defense Advanced Research Projects Agency (DARPA). DARPA has been instrumental in supporting most of our research over the last 22 years and is gratefully acknowledged here. Our overall support has come from the following organizations: " Defense Advanced Research Projects Agency; " Department of Energy; " National Institutes of Health, under National Library of Medicine; " National Science Foundation; " Office of Naval Research; " United States Air Force; " United States Army Research Office " MIT controlled IBM funds under an IBM/MIT joint study contract; Other support of a generally smaller level has come from Apple, Honeywell, Harris Corporation, NASA, and Siemens. p TABLE OF CONTENTS a' VINTRODUCTION 1 CLINICAL DECISION MAKING ) 5 1. Introduction 7 2. Overview of Research Pro 8 3. Critica e roject 9 4. Explanation and Justification by Expert Programs 14 5. Program for the Management of Heart Failure 26 6. Tools for Clinical Decision Analysis 30 COMPUTATION STRUCTURES ") 39 1. Introduction 40 2. Static Dataflow Architecture 40 3. Processing Element Design 40 4. The Enable Memor _- - 42 .1.-a5 A -time Design Methodology 42 /" 6. Fault Detection and Recovery Strategies for a Static dataflow Machine 43 7. The Interaction of Routing Network Traffic and Dataflow Instruction 44 Scheduling 8. The Program Transforming Compiler 45 9. The VIM Project 47 10. Functional Language Implementation on the Connection Machine 50 DISTRIBUTED COMPUTER SYSTEMS' 55 1. Introduction 56 2. TheSWIFT Operating System 56 3. Projects in distributed P,' - - 57 _ts in-Network Protocol Design 58 5. Distributed Name Management 58 6. Extended Reach Networks 59 EDUCATIONAL COMPUTING' 65 1. Overview /66 2. Technology 66 ext 70 ive Studies 71 FUNCTIONAL LANGUAGES AND ARCHITECTURES 73 1. Introduction 75 2. Tagged-Token Da,_low Project._ 77 "3. 1Multiprocessor Emulation Facility Project 82 IMAGINATIVE SYSTEMS - 91 1. Introduction 29 2. The Boston Community Information System A 92 3. Imagine Programming Language 104 INFORMATION MECHANICS 117 1. Overview )118 2. Cellular Automata 7 118 f, ~p~~a'Enal i Concepts to Natural Sciences 119 C 4. Reversible Information Processing: Foundations and Quantum Theory 120 5. Reversible Finite-Difference Equations 121 6. Scientific Exchanges 121 MESSAGE PASSING SEMANTICS) 125 1. Overview 126 2. Objectives ) 126 3_- 126 Current Status 127 5. Future Plans 127 6. Resources and Participants 128 PROGRAMMING METHODOLOGY 129 1. Overview . 130 2. Implementation 130 3-.-Linguistic Isiies'ihiDtlbuted rograms 132 / 4. A Debugging Method Tailored to Atomic Actions 136 Q 5. Distributed Version Management for Read-only Actions 138 6. Reaching Approximate Agreement in the Presence of Faults 143 REAL TIME SYSTEMS ' 153 1155, 2. Shema155 3 . -- , -162 4. VLSI Simulation 166 / 5. Parallel Processing 171 6. The L Computer Architecture 173 7. Personal Workstations 177 THEORY OF COMPUTATION 179 1. Overview 181 . rew Revp 181 THEORY OF DISTRIBUTED SYSTEMS 191 1. Overview 192 2. Individual Progress Reports 192 PUBLICATIONS 211 1 ADMINISTRATION Academic Staff M. Dertouzos Director M. Rivest Associate Director Administrative Staff P. Anderegg Assistant Administrative Officer G. Brown Facilities Officer A. Chow Fiscal Officer J. Hynes Administrative Officer M. Jones Fiscal Officer Support Staff L. Cava~laro B. Pierce R. Cinq-Mars E. Profirio R. Donahue M. Sensale A. Kekejian D. Simmons T. LoDuca C. Stevens J. Mullins P. Vancini T. Novak INTRODUCTION The MIT Laboratory for Computer Science (LCS) is an interdepartmental laboratory whose principal goal is research in computer science and engineering. Founded in 1963 as Project MAC (for Multiple Access Computer and Machine Aided Cognition), the Laboratory developed the Compatible Time Sharing System (CTSS), one of the first time shared systems in the world, and Multics -- an improved time shared system that introduced several new concepts. These two major developments stimulated research activities in the application of on-line computing to such diverse disciplines as engineering, architecture, mathematics, biology, medicine, library science and management. Since that time, the Laboratory's pursuits expanded, leading to pioneering research in Expert Systems, Computer Networks, and Public Cryptography. Today, the Laboratory's research spans a broad front of activities, grouped in four major areas,' The first such area entitled Knowledge Based Systems, volves making programs more intelligent by capturing, representing, and using knov~e ge which is specific to the problem domain. Examples are the use of expert medic nowledge for assistance in diagnosis carried out by the Clinical Decision Makin oup; and the use of solid-state circuit design knowledge for an expert VLSI (ver arge scale integration) design system Q l by the VLSI Design Project. Research in the second and largest area entitled Machines, Languages, and Systems strives to discover and understand computing systems at both the hardware and software levels that open new application areas and/or effect sizable improvements in their ease of utilization and cost effectiveness. New research in this area includes the architecture of very large multiprocessor machines (which tackle a single task, e. speech understanding or weather analysis) by the Computation Structures, Funct al Languages and Architectures, and Real Time Systems Research Groups. Co nuing research includes the analysis and synthesis of languages and operating sy s for use in large geographically distributed systems by the Programming Meth logy and Real Time Systems Groups. Extended networks for such distributed envjonments as well as distributed file servers are studied by the Distributed Comp ter Systems Group. Finally, a key application involving the matching of news nd other community information to individual needs, is pursued by the Imaginative S stems Group. N, The Laboratory's third principal area of research, entitle Theor involves exploration and development of theoretical foundations in computer sci nce, For example, the Theory of Computation Group strives to understand ultimate limits in space and time associated with various classes of algorithms; the semantics of programming languages from both analytical and synthetic viewpoints; the logic of programs; the utility of randomness in computation; concurrent computation and the INTRODUCTION links between mathematics an the privacy/authentication of computer-to-computer messages. Other examples of the retical work involve the study of distributed systems