Table of ContentsList of Figures1. Overview of Advanced Joshua Concepts1.1. The Joshua Protocol of Inference1.2. The Default Implementation of the Protocol1.3. Customizing the Joshua ProtocolIndex2. Storing and Retrieving Knowledge in Joshua: theVirtual Database2.1. What is a Virtual Database?2.2. Predications as Instances2.3. The Joshua Database Protocol2.3.1. The Contract of the Generic Function joshua:insert2.3.2. The Contract of the Generic Functions joshua:ask-data and joshua:fetch2.3.2.1. Signalling a Condition When joshua:ask-data or joshua:fetch Can’t Handle aQuery2.3.3. The Contract of the Generic Function joshua:uninsert2.3.4. The Contract of the Generic Function joshua:clear2.4. Joshua’s Default Database: the Discrimination Net2.4.1. Organization of the Default Discrimination Net3. The Joshua Rule Facilities3.1. Advanced Features of Joshua Rules3.2. The Joshua Rule Compiler3.2.1. The Forward Rule Compiler3.2.1.1. Compiling the Action Part of a Forward Rule3.2.1.2. Forward Rule Triggers: the Rete Network3.2.2. The Backward Rule Compiler3.3. Ordering Rule Execution3.4. Controlling Rule Invocation3.5. The Joshua Rule Indexing Protocol3.5.1. The Contract of the Trigger Adding Functions3.5.2. The Contract of the Trigger Deleting Functions3.5.3. The Contract of the Trigger Locating Functions3.5.4. The Contract of the Trigger Mapping Functions3.5.4.1. Finding Forward Rule Triggers3.5.4.2. Finding Backward Rule Triggers4. The Joshua Question Facilities4.1. Controlling Question Invocation4.2. The Joshua Question Indexing Protocol4.2.1. The Contract of joshua:add-backward-question-trigger4.2.2. The Contract of joshua:delete-backward-question-trigger4.2.3. The Contract of joshua:locate-backward-question-trigger4.2.4. The Contract of joshua:map-over-backward-question-triggers4.2.4.1. Finding Backward Question Triggers5. Truth Maintenance Facilities5.1. The Truth Maintenance Protocol5.1.1. The Contract of the Joshua TMS Protocol Functions5.1.2. The Contract of a Joshua TMS Justification5.1.3. TMS Utility Routines5.1.4. Signalling Contradictions and Managing Backtracking5.1.5. Signalling Truth Value Changes5.2. The Joshua LTMS5.2.1. Clause Justification Structures6. Joshua Metering6.1. Joshua Metering Types6.1.1. Joshua Tell Metering6.1.2. Joshua Ask Metering6.1.3. Joshua Merge Metering6.2. Choosing Joshua Metering Types7. Controlling Data and Rule Indexing7.1. Customizing the Data Index7.1.1. Customizing the Data Index Without Storing Predications7.2. Customizing the Rule Index7.3. Customizing the Rule Compiler7.3.1. Customizing the Matchers Generated by the Rule Compiler8. The Joshua Object Facility8.1. Introduction to the Joshua Object Facility8.2. Basic Capabilities of the Joshua Object Facility8.3. Using Paths to Refer to the Structure of an Object8.4. Type Hierarchy in the Joshua Object Facility8.5. Part-Whole Hierarchy in the Joshua Object Facility8.6. Other Capabilities of Slots8.6.1. Initial Values of Slots8.6.2. Set Valued and Single Valued Slots8.6.3. Slots and Truth Maintenance8.6.4. Slots and Attached Actions8.6.5. Invoking Methods Associated with the Object Associated with a Slot8.6.6. Equalities Between Slot Values8.7. Other Options in Define-Object-Type8.8. The Predicates Used in the Joshua Object Facility9. Joshua Language Dictionary9.1. Dictionary EntriesIndexJoshua Reference Manualiii March 1999 Table of Contents Table of Contents Page 1 Overview of Advanced Joshua Concepts 1 1.1 The Joshua Protocol of Inference 2 1.2 The Default Implementation of the Protocol 2 1.3 Customizing the Joshua Protocol 5 2 Storing and Retrieving Knowledge in Joshua: the Virtual Database 7 2.1 What is a Virtual Database? 7 2.2 Predications as Instances 7 2.3 The Joshua Database Protocol 8 2.3.1 The Contract of the Generic Function joshua:insert 9 2.3.2 The Contract of the Generic Functions joshua:ask-data 10 and joshua:fetch 2.3.3 The Contract of the Generic Function joshua:uninsert 14 2.3.4 The Contract of the Generic Function joshua:clear 14 2.4 Joshua’s Default Database: the Discrimination Net 16 2.4.1 Organization of the Default Discrimination Net 17 3 The Joshua Rule Facilities 23 3.1 Advanced Features of Joshua Rules 24 3.2 The Joshua Rule Compiler 26 3.2.1 The Forward Rule Compiler 27 3.2.2 The Backward Rule Compiler 33 3.3 Ordering Rule Execution 35 3.4 Controlling Rule Invocation 35 3.5 The Joshua Rule Indexing Protocol 36 3.5.1 The Contract of the Trigger Adding Functions 38 3.5.2 The Contract of the Trigger Deleting Functions 38 3.5.3 The Contract of the Trigger Locating Functions 39 3.5.4 The Contract of the Trigger Mapping Functions 41 4 The Joshua Question Facilities 47 4.1 Controlling Question Invocation 47 4.2 The Joshua Question Indexing Protocol 48 4.2.1 The Contract of joshua:add-backward-question-trigger 48 4.2.2 The Contract of joshua:delete-backward-question-trigger 48 4.2.3 The Contract of joshua:locate-backward-question-trigger 49 4.2.4 The Contract of joshua:map-over-backward-question-50 triggersiv Table of Contents March 1999 5 Truth Maintenance Facilities 53 5.1 The Truth Maintenance Protocol 54 5.1.1 The Contract of the Joshua TMS Protocol Functions 54 5.1.2 The Contract of a Joshua TMS Justification 55 5.1.3 TMS Utility Routines 56 5.1.4 Signalling Contradictions and Managing Backtracking 57 5.1.5 Signalling Truth Value Changes 63 5.2 The Joshua LTMS 65 5.2.1 Clause Justification Structures 65 6 Joshua Metering 73 6.1 Joshua Metering Types 73 6.1.1 Joshua Tell Metering 73 6.1.2 Joshua Ask Metering 75 6.1.3 Joshua Merge Metering 76 6.2 Choosing Joshua Metering Types 77 7 Controlling Data and Rule Indexing 79 7.1 Customizing the Data Index 81 7.1.1 Customizing the Data Index Without Storing Predications 85 7.2 Customizing the Rule Index 88 7.3 Customizing the Rule Compiler 92 7.3.1 Customizing the Matchers Generated by the Rule Compiler 102 8 The Joshua Object Facility 105 8.1 Introduction to the Joshua Object Facility 105 8.2 Basic Capabilities of the Joshua Object Facility 107 8.3 Using Paths to Refer to the Structure of an Object 109 8.4 Type Hierarchy in the Joshua Object Facility 110 8.5 Part-Whole Hierarchy in the Joshua Object Facility 112 8.6 Other Capabilities of Slots 113 8.6.1 Initial Values of Slots 113 8.6.2 Set Valued and Single Valued Slots 113 8.6.3 Slots and Truth Maintenance 114 8.6.4 Slots and Attached Actions 114 8.6.5 Invoking Methods Associated with the Object Associated 115 with a Slot 8.6.6 Equalities Between Slot Values 116