Knowledge Systems. T&chnische Hochschule Darmstadt FACHBEREICH INFORMATIK B1BLIOTHEK. Inventar-Nr: Standout

Transcription

1 Introduction to Knowledge Systems Mark Stefik T&chnische Hochschule Darmstadt FACHBEREICH INFORMATIK B1BLIOTHEK Inventar-Nr: Sachgebiete: Standout M:2.L~^r.ff. Morgan Kaufmann Publishers, Inc San Francisco, California

2 Contents Foreword Edward A. Feigenbaum xiii Preface xv Notes on the Exercises xix INTRODUCTION AND OVERVIEW 1 PARTI FOUNDATIONS 19 CHAPTER 1 Symbol Systems Symbols and Symbol Structures What Is a.symbol? Designation Causal Coupling Cognitive and Document Perspectives of Symbols Summary and Review 32 Exercises for Section Semantics: The Meanings of Symbols Model Theory and Proof Theory Reductionist Approaches for Composing Meanings Terminology for Graphs and Trees Graphs as Symbol Structures The Annotation Principle and Metalevel Notations Different Kinds of Semantics Summary and Review 59 Exercises for Section

3 vi CONTENTS 1.3 Modeling: Dimensions of Representation Fidelity and Precision Abstractions and Implementations Primitive and Derived Propositions Explicit and Implict Representations Representation and Canonical Form Using Multiple Representations Representation and Parallel Processing Space and Time Complexity Structural Complexity Summary and Review 101 Exercises for Section Programs: Patterns, Simplicity, and Expressiveness Using Rules to Manipulate Symbols Treating Programs as Data Manipulating Expressions for Different Purposes Pattern Matching Expressiveness, Defaults, and Epistemological Primitives The Symbol Level and the Knowledge Level Summary and Review 130 Exercises for Section Quandaries and Open Issues 136 CHAPTER 2 Search and Problem Solving Concepts of Search Solution Spaces and Search Spaces Terminology about Search Criteria Representing Search Spaces as Trees Preview of Search Methods Summary and Review 158 Exercises for Section Blind Search Depth-First and Breadth-First Search Top-Down and Bottom-Up Search: A Note on Terminology Simple and Hierarchical Generate-and-Test A Sample Knowledge System Using Hierarchical Generate-and-Test Simple and Backtracking Constraint Satisfaction Summary and Review 193 Exercises for Section

4 CONTENTS vii 2.3 Directed Search Simple Match Means-Ends Analysis Hierarchical Match and Skeletal Planning Hill Climbing and Best-first Search Shortest-Path Methods A* and Related Methods Summary and Review 248 Exercises for Section Hierarchical Search Two-Level Planning Planning with Multiple Abstraction Levels Planning with Imperfect Abstractions Summary and Review 279 Exercises for Section Quandaries and Open Issues 287 CHAPTER 3 Knowledge and Software Engineering Understanding Knowledge Systems in Context The Terminology of Knowledge Systems and Expertise Knowledge Systems and Document Systems: Five Scenarios Preview of Knowledge Acquisition Topics Summary and Review 312 Exercises for Section Formulating Expertise Conducting Initial Interviews Taking Protocols Characterizing Search Spaces Adapting Protocol Analysis for Knowledge Systems Summary and Review 330 Exercises for Section Collaboratively Articulating Work Practices Variations in Processes for Interview and Analysis Documenting Expertise Engineering Software and Organizations Summary and Review 358 Exercises for Section

5 viii CONTENTS 3.4 Knowledge versus Complexity MYCIN: Study of a Classic Knowledge System The Knowledge Hypothesis and the Qualification Problem Summary and Review 389 Exercises for Section Open Issues and Quandaries PART II THE SYMBOL LEVEL 403 CHAPTER 4 Reasoning about Time 4.1 Temporal Concepts Timeline Representations A Discrete Model of Transactions in the Balance of an Account Continuous versus Discrete Temporal Models Temporal Uncertainty and Constraint Reasoning Partial Knowledge of Event Times Arc Consistency and Endpoint Constraints Time Maps and Scheduling Problems The Interface between a Scheduler and a Temporal Database Branching Time Summary and Review 423 Exercises for Chapter Open Issues and Quandaries CHAPTER 5 Reasoning about Space Spatial Concepts Spatial Search Simple Nearest-First Search Problems with Uniform-Size Regions Quadtree Nearest-First Search Multi-Level Space Representations Reasoning about Shape The Piano Example: Using Multiple Representations of Space Reasoning for the Piano Movers Rendering a Piano The Action of a Piano

6 CONTENTS ix 5.5 Summary and Review 452 Exercises for Chapter Open Issues and Quandries 458 CHAPTER 6 Reasoning about Uncertainty and Vagueness Representing Uncertainty Concepts about Uncertainty The Certainty-Factor Approach The Dempster-Shafer Approach Probability Networks Summary and Conclusions 504 Exercises for Section Representing Vagueness Basic Concepts of Fuzzy Sets Fuzzy Reasoning Summary and Conclusions 531 Exercises for Section Open Issues and Quandries 533 PART III THE KNOWLEDGE LEVEL 541 CHAPTER 7 Classification Introduction Regularities and Cognitive Economies Models for Classification Domains A Computational Model of Classification Model Variations and Phenomena Pragmatics in Classification Systems Summary and Review 556 Exercises for Section Case Studies of Classification Systems Classification in MYCIN Classification in MORE Classification in MOLE Classification in MDX Classification in PROSPECTOR Summary and Review 586 Exercises for Section

7 x CONTENTS 7.4 Knowledge and Methods for Classification Knowledge-Level and Symbol-Level Analysis of Classification Domains MC-1: A Strawman Generate-and-Test Method MC-2: Driving from Data to Plausible Candidates MC-3: Solution-Driven Hierarchical Classification MC-4: Data-Driven Hierarchical Classification Method Variations for Classification Summary and Review 602 Exercises for Section Open Issues and Quandaries 604 CHAPTER 8 Configuration Introduction Configuration Models and Configuration Tasks Defining Configuration Models for Configuration Domains Computational Models of Configuration Phenomena in Configuration Problems Summary and Review 620 Exercises for Section Case Studies of Configuration Systems Configuration in XCON Configuration in M1/MIC0N Configuration in MYCIN's Therapy Task Configuration in VT Configuration in COSSACK Summary and Review 650 Exercises for Section Methods for Configuration Problems Knowledge-Level and Symbol-Level Analysis of Configuration Domains MCF-1: Expand and Arrange MCF-2: Staged Subtasks with Look-Ahead MCF-3: Propose-and-Revise Summary and Review 665 Exercises for Section Open Issues and Quandaries 667

8 CONTENTS xi CHAPTER 9 Diagnosis and Troubleshooting Introduction Diagnosis and Troubleshooting Scenarios Dimensions of Variation in Diagnostic Tasks Models for Diagnosis Domains Recognizing Abnormalities and Conflicts Generating and Testing Hypotheses Discriminating among Hypotheses Summary and Review 700 Exercises for Section Case Studies of Diagnosis and Troubleshooting Systems Diagnosis in DARN Diagnosis in INTERNIST Diagnosis in CASNET/GLAUCOMA Diagnosis in SOPHIE III Diagnosis in GDE Diagnosis in SHERLOCK Diagnosis in XDE Summary and Review 759 Exercises for Section Knowledge and Methods for Diagnosis Plan Models for Diagnosis Classification Models for Diagnosis Causal and Behavioral Models for Systems Summary and Review 768 Exercises for Section Open Issues and Quandaries 771 APPENDIX A Annotated Bibliographies by Chapter 776 APPENDIX B Selected Answers to Exercises 811 Index 853