CLIPS Common Object Language COOL

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CLIPS Common Object LanguageCOOL

• Bob McKay
• School of Computer Science and Engineering
• College of Engineering
• Seoul National University

2
Course Review

• Knowledge Representation and Reasoning 9852
• http//web.cse.snu.ac.kr/survey/

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Outline

• Higher Order Logics
• Ontologies
• Actions
• Representing Belief, Knowledge,

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CLIPS Object-Oriented Language (COOL)

• A powerful object-oriented language
• Built on top of the basic production-rule system
• Relationship between COOL and CLIPS is similar to
  that between C and C

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COOL Class Definitions

• (defclass ltclassgt
• (is-a ltdirect superclassesgt)
• (role ltconcrete abstractgt)
• (slot ltslot-namegt (ltslot facetsgt)
• (default ltdefaultgt)))
• Notes
• There is only one inheritance relation (is-a)
• Multiple inheritance is permitted

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COOL Class Examples

• (defclass QUADRILATERAL
• (is-a Object))
• (defclass KITE
• (is-a QUADRILATERAL))
• (defclass TRAPEZOID
• (is-a QUADRILATERAL))
• (defclass PARALLELOGRAM
• (is-a TRAPEZOID))
• (defclass ISOSCELES-TRAPEZOID
• (is-a TRAPEZOID))
• (defclass RECTANGLE
• (is-a PARALLELOGRAM ISOSCELES-TRAPEZOID))
• (defclass RHOMBUS
• (is-a PARALLELOGRAM KITE))
• (defclass SQUARE
• (is-a RHOMBUS RECTANGLE))

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COOL Built-in Classes

• OBJECT
• USER
• INITIAL-OBJECT
• PRIMITIVE
• NUMBER
• INTEGER
• FLOAT

• INSTANCE
• INSTANCE-NAME
• INSTANCE-ADDRESS
• ADDRESS
• FACT-ADDRESS
• MULTIFIELD
• LEXEME
• SYMBOL
• STRING

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COOL Class Instances

• Creation
• An instance of a class is created with
  make-instance
• (make-instance ltinstance-namegt of ltclassgt
  ltslot-overridegt)
• (make-instance Dorky of DUCK (sound quack))
• Deletion
• (reset)
• (unmake-instance ltinstance namegt)
• send instance a delete message

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COOL Slots

• Slots are created along with classes
• Their values are set
• either at the time of creation of an instance
• or at a later stage by the sending of a message
• Except that values of slots with shared facet
  are shared by all instances of the class
• Like static fields

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COOL Slots

• Facets
• Facets are aspects of a slot, which determine the
  values it may have
• Defaults
• Defaults may be either
• Static
• the default is evaluated at the time the class is
  created
• Dynamic
• the default is evaluated each time an instance is
  created

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COOL Slots

• Cardinality
• Cardinality may be
• multiple - the facet can hold multiple values
• Messages
• Format
• (send ltinstance namegt ltmessagegt)
• (send Dorky delete)
• (send Dorky (put-sound quack))
• Correspond to method calls in Java

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COOL Handlers

• Handlers are the means by which objects respond
  to messages
• Correspond to Java methods
• (defmessage-handler
• ltclassgt
• ltmessagegt handler-type
• (ltparametersgt)
• (ltactionsgt))
• (defmessage-handler NUMBER (?arg)
• ( ?self ?arg))

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COOL Handler Classes

• around
• set up environment for other handler
• (executes partly before and partly after other
  handlers
• Before
• auxiliary work before primary
• Primary
• The main handler
• After
• clean-up work after primary

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COOL Daemons

• In CLIPS terminology, daemons are handlers which
  execute on the occurrence of some basic action
• initialisation
• deletion
• get
• put
• Conceptually, they are automatically sent a
  message on occurrence of the relevant event