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Frames

Frames. Lecture 20. What is a Frame?. A frame is a prototype of a concept Denoting the attributes of the concept The class of objects or concepts to which the concept in question belongs And some more things ……… An instance of a frame is a representation of a SPECIFIC object

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Frames

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  1. Frames Lecture 20 @Anupam Basu

  2. What is a Frame? • A frame is a prototype of a concept • Denoting the attributes of the concept • The class of objects or concepts to which the concept in question belongs • And some more things ……… • An instance of a frame is a representation of a SPECIFIC object • Instantiation of a frame @Anupam Basu

  3. Example • Fido is a dog • The concept dog • Fido is a particular dog • How can we represent the concept/notion of the creature “dog”? @Anupam Basu

  4. Slot name Dog { is a: mammal; no._of_legs: 4; type_of_teeth: sharp; has_tail: yes; color_of_skin: ; owner: ; : : } Slot value @Anupam Basu

  5. Fido { is a: Dog; no._of_legs: 4; type_of_teeth: sharp; has_tail: yes; color_of_skin: Black; owner: Rahim; : : } @Anupam Basu

  6. Object-Attribute-Value <o,a,v> • An instance of a frame denotes an object • A Frame denotes a class to which the object belongs • The slots denote the attributes of the object • The slots can be of different types • The slots are instantiated with values @Anupam Basu

  7. Semantic Net to Frame Animal Elephant Nellie head Africa @Anupam Basu

  8. Slots • Slots denote attributes • Attributes are typed • Some values are defined in the frame definition (already instantiated) • Some values are defined in the instances only • Instantiated slots define facts – may be used to answer queries @Anupam Basu

  9. What are there in a slot? • Values • Types • Constraints over possible values • Predicates • Daemons / functions • Compare with object oriented systems • Slots can be structured – frames within slots – pointers to frames @Anupam Basu

  10. Boy @Anupam Basu

  11. Boy If added test (constraint) @Anupam Basu

  12. Tom @Anupam Basu

  13. Predicates in a Slot • Two types in general • If needed • If added • If needed predicates state how to find/compute a value • If added predicates are used to check constraints on the values • Can be used for consistency checking as well. @Anupam Basu

  14. Generic Values • Does Tom drink milk? • The answer is not in the instance description of Tom. @Anupam Basu

  15. Tom is an instance of a Boy • Also, Boy is a Human Being • In the description of Human Beings, we have “Human Beings drink milk” • All human beings drink milk. • The answer can therefore be INHERITED @Anupam Basu

  16. Generic values are values which will hold true for all subclasses of the class and all instances of the class. • Hence, the generic values can be inherited down the hierarchy. • Tom has a pen. Does he need ink? @Anupam Basu

  17. Default Value • With which hand does Tom write? • Again the answer is not in the description of Tom. @Anupam Basu

  18. Boy If added test (constraint) @Anupam Basu

  19. Since we are not told that Tom is left handed, we will assume that Tom writes with right hand. • Again inheritance of the Default Value @Anupam Basu

  20. Inheritance • The known values can be inherited from the parents unless more specific information is available with the child. • In the super class (parent) the generic values and the default values are specified. • The generic values are retained. • Default values may be overwritten. @Anupam Basu

  21. Multiple Inheritance • A class or an instance may be a child of multiple parents. • What to inherit? @Anupam Basu

  22. Teacher Politician Top-Priority Teacher- Politician Vote Bank Quality Education @Anupam Basu ??

  23. Wrong Organization Automobile Two Wheeler Has-wheels 4 2 Scooter @Anupam Basu ??

  24. Correct Organization Automobile Has-wheels Two Wheeler 4 2 Scooter @Anupam Basu

  25. Inference in a Frame • Look for candidate frames or instances • Look for the availability of values • If available – solved • Else go to the preceding level and so on • If soled at a higher level, try to have more specific answer going down the hierarchy through another branch @Anupam Basu

  26. Answering a Query Rt.handed Batsman Opener Batt. Avg. Sehwag With which hand does Sehwag bat? @Anupam Basu

  27. Shapes Triangle Rectangle Circle Equilateral Isoceles @Anupam Basu

  28. Similarity Measure • Define similarity function based on the matches in <attribute value pair> • Degree of mismatch may have limited penalty • For key values one mismatch may rule out a match @Anupam Basu

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