Frames in Artificial Intelligence

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

Example

• Fido is a dog
• The concept dog
• Fido is a particular dog
• How can we represent the concept/notion of the creature "dog"?

Dog
 {
         is a : mammal;
         no._of_legs: 4;
         type_of_teeth: sharp;
         has_tail: yes;
         color_of_skin:   ;
         owner:               ;
          .
          .
          .
 }

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


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

Semantic Net to Frame

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

What are there in a slot ?

• Values
• Types
• Constraints over possible values
• Predicates
• Daemons/function
• Compare with object oriented systems
• Slots can be structured - frames within slots - pointers to frames

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.

Generic Values

• Does Tom drink milk ?
• The answer is not in the instance description og Tom.

→ 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

→ 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 ?

Default Value

• With which hand does Tom write ?
• Again the answer is not in the description of Tom.
• 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