Frame-Based Representation Frame: stereotypical knowledge knowledge of some concept. Bird Frame Name Properties CLASS FRAME Tweety Frame Name Properties INSTANCE FRAME

Frames Hold Structure and Behavior of a class of objects/concepts Structure properties/data/attributes Behavior methods, rules defining how instances of the class typically behave Generic structure and behavior defines at class level is specified in instances

Inheritance Structural and behavioral properties are inherited from super-class to sub-classes subclasses automatically carry the structure an behavior of super-class exception handling (birds fly, but penguins do not) multiple inheritance Birds Bird 1 Bird 2 Robins Canaries Bird 3 Bird 4 Sparrows Bird 6 Bird 5

Multiple Inheritance class Bird color eats flies... class Pet name veterinarian... class PetBird color eats flies name veterinarian talks... class Person age weight... class Employee phone# salary... Instance Jack age weight phone# salary

Facets provide further information on a property/attribute –define constraints on property value (data type, range of values, etc.) –how to obtain a value for a property (IF-NEEDED method) –what to do if a value changes (IF-CHANGED method)

Properties and Facets: Example Object name: Refrigerator Class:Home Appliances - Initialize - from Database - from Procedure - Expert Rules - User specified - by Inheritance - Message passing from other objects

Communication between objects Defrost Timer Refrigerator Heating Coil IF-CHANGED methods

Rule Interaction with Objects Frame properties as data IF Humans.Legs = 2IF Jack.Legs=2 THEN humans can walkTHEN Jack can walk Modifying a property value IF Jack likes to swim THEN Jacks.Sports = swimming Creating a new instance IF Lucy is mad at Jack because he doesn’t like hiking THEN MAKE Frame Bob Instance-of Humans WITH Sports = Hiking Deleting a frame IF Lucy is really mad at Jack THEN RETRACT Frame Jack

JackLucy Bob Humans

Pattern Matching ?xx denotes variable Frame ?x instance-of Humans WITH Residence = Pittsburgh WITH Age = ?Age IF Frame ?x instance-of Humans WITH Residence = Pittsburgh WITH Age = ?Age THEN Frame ?x WITH Age = ?Age + 5 IF Frame ?person1 WITH Sex = Male WITH Sports = ?sports1 AND Frame ?person2 WITH Sex = Female WITH Sports = ?sports1 THEN Frame ?person1 WITH Likes = ?person2