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Frame-based Expert Systems

سید ضیاء الدین البرزی زیر نظر جناب دکتر حلاوتی. Frame-based Expert Systems. One common methods used for representing knowledge in an expert systems. How a FB experts system uses frames combined with techniques borrowed from OOP to create powerful tool for addressing complex problems.

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Frame-based Expert Systems

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  1. سید ضیاء الدین البرزی زیر نظر جناب دکتر حلاوتی Frame-based Expert Systems

  2. One common methods used for representing knowledge in an expert systems. How a FB experts system uses frames combined with techniques borrowed from OOP to create powerful tool for addressing complex problems. Developing a FB system Collection of related objects that describe the problem. Introduction

  3. The motivation for current work in FB expert systems has its roots in earlier human problem-solving studies by cognitive psychologists. Bartlett (1932) Schema : is a unit of knowledge that contains info. About some concept  automobile Following this idea Minsky propose Frame (1975) Frame : is a data structure for encoding in a computer typical info. On some concept. overview

  4. Frame = Name + Slots + Values + Procedures Object Oriented Programming Overview (cont.) CONCEPT INSTANCE Car  Your Car

  5. A computer program that process problem-specific information contained in working memory with a set of frames contained in the knowledge base, using an inference engine to infer new information. FB Systems ≡ RB Systems Relationships between frames is expressed by child-to-parent distinction Frame-based systems

  6. Frame world of humans Names Humans Class Properties(slots) Values Facets Men Women Subclass Kathy Jack Bob Lucy Instances Rules Goal agenda

  7. A collection of objects that share some common properties. Anatomy of a class Class of Humans

  8. Subclasses are classes that represent subset of higher level classes. • Three kind of relationship among classes and subclasses. • Generalization  Kind of… • Aggregation  Part of… • Association  Semantic… Anatomy of a subclass

  9. Generalization Anatomy of a subclass (cont.) Vehicle Kind of Cars Plane Boat

  10. Aggregation Anatomy of a subclass (cont.) Car Part of Door Engine Battery

  11. Association Anatomy of a subclass (cont.) I own Semantic Cars Houses Assets

  12. Procedures store in Facet We can add more properties Anatomy of a subclass (cont.) Class of men

  13. A specific object from a class of objects. Anatomy of instance Object jack

  14. The properties used in frames describe the major features or att. Of concept or object. • Properties = Form a set of object-attribute-values • Property values = Data assign to a given property • Values = Numeric, symbolic, boolean. Another feature  facets Anatomy of properties

  15. Anatomy of properties (cont.) Refrigerator Object

  16. Inheritance • Process by which the characteristics of parent frame are assume by its child frame • Exception handling • Don’t forget … • Multiple inheritance • Jack is instance of Men & jack is instance of Employee …

  17. Extended knowledge about a frame’s property. • Facet extend the info. In • Type • Default • Documentation • Constraint • Minimum cardinality • Maximum cardinality • If needed • If changed Facets

  18. Sensor object with facets

  19. Methods • A procedure attached to an object, that will be executed whenever requested  (if needed, if changed) • Encapsulation • Hiding of information (use w/o worrying about opration ) • Communication between objects • One Obj. use another one when if needed or changed (For example  refrigerator + defrost timer + heating coil) • Message passing …

  20. A signal to an object to which the object responds by executing a method. • Ask a request from your friend. • Draw message to a circle obj. • Sometimes named handler. • According to shell  Send, Sendmsg, SendMessage. • (Send message-name object-name arguments) Message passing

  21. Example of message-passing Bobs--Car Age method Args (year) 20 Year 1970 1990 message 1990 Jacks--Car Age method 10 Args (year) Year 1980

  22. Inheriting behavior • Bobs-car.year • Writing general methods • Self.property name to self, object’s property to property. • Rule interaction with objects • Frame properties as Data …

  23. Modifying a property value • IF jack likes to swim THEN Jack.Sports=Swimming • Creating a New Instance • IF Lucy is mad at jack because he doesn’t like walking THEN MAKE Frame BOB Instance of Humans WITH Sports=walking • Delete an instance • IF Lucy is really mad at Jack THEN RETRACT Frame JACK …

  24. Pattern matching Using matches in rule’s conclusion Using rules with variables

  25. Complex variable Matching Using rules with variables (Cont.)

  26. Question… ?

  27. Thanks for you consideration

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