CLIPS Basic Programming Guide

Version 6.24 June 15th 2006

CONTENTS

License Information....................................................................................................................... i

Preface............................................................................................................................................ iii

Acknowledgements...................................................................................................................... vii

Section 1 ‑ Introduction................................................................................................................ 1

Section 2 ‑ CLIPS Overview......................................................................................................... 3

2.1 Interacting with CLIPS........................................................................................................ 3

2.1.1 Top Level Commands................................................................................................. 3

2.1.2 Automated Command Entry and Loading................................................................... 4

2.1.3 Integration with Other Languages............................................................................... 5

2.2 Reference Manual Syntax.................................................................................................... 5

2.3 Basic Programming Elements.............................................................................................. 6

2.3.1 Data Types.................................................................................................................. 6

2.3.2 Functions.................................................................................................................... 9

2.3.3 Constructs................................................................................................................. 10

2.4 Data Abstraction................................................................................................................ 10

2.4.1 Facts.......................................................................................................................... 10

2.4.1.1 Ordered Facts................................................................................................... 11

2.4.1.2 Non‑ordered Facts........................................................................................... 12

2.4.1.3 Initial Facts....................................................................................................... 13

2.4.2 Objects...................................................................................................................... 13

2.4.2.1 Initial Objects................................................................................................... 14

2.4.3 Global Variables....................................................................................................... 14

2.5 Knowledge Representation................................................................................................ 15

2.5.1 Heuristic Knowledge – Rules................................................................................... 15

2.5.2 Procedural Knowledge.............................................................................................. 16

2.5.2.1 Deffunctions.................................................................................................... 16

2.5.2.2 Generic Functions............................................................................................ 16

2.5.2.3 Object Message‑Passing.................................................................................. 16

2.5.2.4 Defmodules...................................................................................................... 17

2.6 CLIPS Object‑Oriented Language..................................................................................... 17

2.6.1 COOL Deviations from a Pure OOP Paradigm........................................................ 17

2.6.2 Primary OOP Features.............................................................................................. 18

2.6.3 Instance‑set Queries and Distributed Actions........................................................... 18

Section 3 ‑ Deftemplate Construct............................................................................................. 19

3.1 Slot Default Values............................................................................................................ 20

3.2 Slot Default Constraints for Pattern‑Matching................................................................... 20

3.3 Slot Value Constraint Attributes........................................................................................ 21

3.4 Implied Deftemplates......................................................................................................... 21

Section 4 ‑ Deffacts Construct.................................................................................................... 23

Section 5 ‑ Defrule Construct..................................................................................................... 25

5.1 Defining Rules................................................................................................................... 25

5.2 Basic Cycle Of Rule Execution.......................................................................................... 26

5.3 Conflict Resolution Strategies............................................................................................ 27

5.3.1 Depth Strategy.......................................................................................................... 27

5.3.2 Breadth Strategy........................................................................................................ 27

5.3.3 Simplicity Strategy.................................................................................................... 27

5.3.4 Complexity Strategy.................................................................................................. 28

5.3.5 LEX Strategy............................................................................................................ 28

5.3.6 MEA Strategy........................................................................................................... 29

5.3.7 Random Strategy....................................................................................................... 29

5.4 LHS Syntax....................................................................................................................... 31

5.4.1 Pattern Conditional Element...................................................................................... 31

5.4.1.1 Literal Constraints............................................................................................ 32

5.4.1.2 Wildcards Single‑ and Multifield..................................................................... 34

5.4.1.3 Variables Single‑ and Multifield...................................................................... 36

5.4.1.4 Connective Constraints.................................................................................... 38

5.4.1.5 Predicate Constraints........................................................................................ 41

5.4.1.6 Return Value Constraints................................................................................. 43

5.4.1.7 Pattern‑Matching with Object Patterns............................................................. 44

5.4.1.8 Pattern‑Addresses............................................................................................ 47

5.4.2 Test Conditional Element.......................................................................................... 47

5.4.3 Or Conditional Element............................................................................................. 49

5.4.4 And Conditional Element.......................................................................................... 50

5.4.5 Not Conditional Element........................................................................................... 51

5.4.6 Exists Conditional Element....................................................................................... 52

5.4.7 Forall Conditional Element........................................................................................ 54

5.4.8 Logical Conditional Element..................................................................................... 56

5.4.9 Automatic Addition and Reordering of LHS CEs..................................................... 59

5.4.9.1 Rules Without Any LHS Pattern CEs.............................................................. 59

5.4.9.2 Test and Not CEs as the First CE of an And CE.............................................. 59

5.4.9.3 Test CEs Following Not CEs........................................................................... 60

5.4.9.4 Or CEs Following Not CEs............................................................................. 61

5.4.9.5 Notes About Pattern Addition and Reordering................................................ 61

5.4.10 Declaring Rule Properties....................................................................................... 61

5.4.10.1 The Salience Rule Property............................................................................ 62

5.4.10.2 The Auto‑Focus Rule Property...................................................................... 63

Section 6 ‑ Defglobal Construct.................................................................................................. 65

Section 7 ‑ Deffunction Construct.............................................................................................. 71

Section 8 ‑ Generic Functions..................................................................................................... 73

8.1 Note on the Use of the Term Method................................................................................. 73

8.2 Performance Penalty of Generic Functions........................................................................ 74

8.3 Order Dependence of Generic Function Definitions.......................................................... 74

8.4 Defining a New Generic Function..................................................................................... 74

8.4.1 Generic Function Headers......................................................................................... 75

8.4.2 Method Indices......................................................................................................... 75

8.4.3 Method Parameter Restrictions................................................................................. 76

8.4.4 Method Wildcard Parameter...................................................................................... 77

8.5 Generic Dispatch................................................................................................................ 79

8.5.1 Applicability of Methods Summary.......................................................................... 79

8.5.2 Method Precedence................................................................................................... 80

8.5.3 Shadowed Methods.................................................................................................. 83

8.5.4 Method Execution Errors.......................................................................................... 83

8.5.5 Generic Function Return Value................................................................................. 83

Section 9 ‑ CLIPS Object Oriented Language (COOL)........................................................... 85

9.1 Background........................................................................................................................ 85

9.2 Predefined System Classes................................................................................................ 85

9.3 Defclass Construct............................................................................................................. 86

9.3.1 Multiple Inheritance.................................................................................................. 87

9.3.1.1 Multiple Inheritance Rules............................................................................... 88

9.3.2 Class Specifiers......................................................................................................... 90

9.3.2.1 Abstract and Concrete Classes......................................................................... 90

9.3.2.2 Reactive and Non‑Reactive Classes................................................................. 90

9.3.3 Slots.......................................................................................................................... 90

9.3.3.1 Slot Field Type................................................................................................. 91

9.3.3.2 Default Value Facet.......................................................................................... 91

9.3.3.3 Storage Facet.................................................................................................... 92

9.3.3.4 Access Facet.................................................................................................... 93

9.3.3.5 Inheritance Propagation Facet.......................................................................... 94

9.3.3.6 Source Facet..................................................................................................... 95

9.3.3.7 Pattern‑Match Reactivity Facet......................................................................... 96

9.3.3.8 Visibility Facet................................................................................................. 97

9.3.3.9 Create‑Accessor Facet...................................................................................... 98

9.3.3.10 Override‑Message Facet................................................................................ 99

9.3.3.11 Constraint Facets............................................................................................ 99

9.3.4 Message‑handler Documentation............................................................................ 100

9.4 Defmessage‑handler Construct........................................................................................ 101

9.4.1 Message‑handler Parameters................................................................................... 103

9.4.1.1 Active Instance Parameter.............................................................................. 103

9.4.2 Message‑handler Actions........................................................................................ 104

9.4.3 Daemons................................................................................................................. 106

9.4.4 Predefined System Message‑handlers..................................................................... 106

9.4.4.1 Instance Initialization...................................................................................... 106

9.4.4.2 Instance Deletion............................................................................................ 107

9.4.4.3 Instance Display............................................................................................. 108

9.4.4.4 Directly Modifying an Instance...................................................................... 108

9.4.4.5 Modifying an Instance using Messages......................................................... 109

9.4.4.6 Directly Duplicating an Instance.................................................................... 109

9.4.4.7 Duplicating an Instance using Messages........................................................ 110

9.4.4.8 Instance Creation............................................................................................ 110

9.5 Message Dispatch............................................................................................................ 110

9.5.1 Applicability of Message‑handlers.......................................................................... 111

9.5.2 Message‑handler Precedence.................................................................................. 111

9.5.3 Shadowed Message‑handlers.................................................................................. 112

9.5.4 Message Execution Errors...................................................................................... 112

9.5.5 Message Return Value............................................................................................ 113

9.6 Manipulating Instances.................................................................................................... 113

9.6.1 Creating Instances................................................................................................... 113

9.6.1.1 Definstances Construct.................................................................................. 115

9.6.2 Reinitializing Existing Instances..............................................................................