Artificial Intelligence - Old Questions

6.  Define knowledge representation system. How knowledge is represented using semantic networks? Illustrate with an example.

Knowledge representation (KR) is the study of how knowledge about the world can be represented and what kinds of reasoning can be done with that knowledge. Knowledge representation is the method used to encode knowledge in Intelligent Systems.

Since knowledge is used to achieve intelligent behavior, the fundamental goal of knowledge representation is to represent knowledge in a manner as to facilitate inferencing (i.e. drawing conclusions) from knowledge. A successful representation of some knowledge must, then, be in a form that is understandable by humans, and must cause the system using the knowledge to behave as if it knows it.

Semantic Network Representation

Semantic networks can

    - show natural relationships between objects/concepts

    - be used to represent declarative/descriptive knowledge

Knowledge is represented as a collection of concepts, represented by nodes. Thus, semantic networks are constructed using nodes linked by directional lines called arcs

A node can represent a fact description

    - physical object

    - concept

    - event

An arc (or link) represents relationships between nodes. There are some 'standard' relationship types

    - 'Is-a' (instance relationship): represent class/instance relationships

    - 'Has-a' (part-subpart relationship): identify property relationships

Example: