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