Knowledge Representation is a way to transform human knowledge to machine understandable format.

Knowledge representation formalizes and organized the knowledge required to build an expert system.

A number of knowledge Representation techniques have been devised:

Production Rules:

A rule is a condition and an action associated with it. Aathe condition part is identified by keyword “IF”. It lists a set of conditions in some logical combination. Actions are specified in “THEN” part.

As the IF part is satisfied: then THEN part actions can be taken. The piece of knowledge represented by the production rule is used to produce the line of reasoning.

As human thinking is evolved on the basis of situation-> conclusion or condition -> action basis, this Model is predominantly used representing knowledge in ES.

Semantic nets:

A semantic net are semantic network is a knowledge representation technique used for propositional information.

Here, the knowledge is represented as as objects and relationships between objects. They are two dimensional representations of knowledge.

Representation provide basic structure for organizing knowledge. It uses graphical notations to draw the networks.

Semantic nets consists of nodes, links and link lables. Objects are denoted by nodes of graph while links indicate relations among the objects.

Nodes appear as circles around ellipses or rectangles to represent objects such as physical objects, concepts or situations. Links are drawn as arrows to express the relationship between objects, and link labels specify specifications of relationships.

Relationships can be off two types “IS-A” or “HAS” relationship. IS-A relationship stands for on object being part of other related object. And HAS-A relationship indicated on object consists of the other related object t.

These relationships are nothing but superclass subclass relationships. It is assumed that all members of a subclass will inherit all the properties of their superclass. That’s how semantic network allows efficient representations of inheritance reasoning.

Frames:

Frames provide a convenient structure for representing objects that are typical to stereotypical situations.

Frame is a type of schema used in many Artificial Intelligence applications including vision and natural language processing. Frames are also useful for representing common sense knowledge.

Frames can represent concepts, situations, attributes of concepts, relationships between concepts, and also procedures to explain their relationships. It allows nodes to have structures and hence is regarded as 3-D representations of knowledge.

A frame is also known as unit, schema, or list. Typically, a frame consists of a list of properties of the object and associated values for the properties; similar to the fields and values; also called as slots and slot filters. The contents of slot can be a string, number, functions, procedures, etc.

A frame is a group of slots and fillers that defines a stereotypical object. Rather than a single frame, a frame systems usually have collection of frames connected to each other.