@Anupam Basu Frames Lecture 20

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

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

@Anupam Basu Object-Attribute-Value 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 Semantic Net to Frame Nellie Elephant Africa Animal head

@Anupam Basu 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 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 is_aHuman _being name age height stays_at studies_in grades Boy string Int<=15 Float< 7.0 Int string *results

@Anupam Basu is_aHuman _being name age height stays_at studies_in grades Boy If needed compute CGPA (Boy, results) If added test (constraint)

@Anupam Basu instance_ofBoy nameTom Smith age12 height 5 stays_at15 Park Avenue studies_inBright Academy grades Tom If needed compute CGPA (Tom, results)

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

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

@Anupam Basu is_aHuman _being name age height stays_at studies_in grades writes withright hand * Boy If needed compute CGPA (Boy, results) If added test (constraint)

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

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

@Anupam Basu Scooter AutomobileTwo Wheeler 4 2 Has- wheels ?? Wrong Organization

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

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

@Anupam Basu Shapes Triangle RectangleCircle EquilateralIsoceles

@Anupam Basu Similarity Measure Define similarity function based on the matches in Degree of mismatch may have limited penalty For key values one mismatch may rule out a match