Knowledge representation

Knowledge representation is a central problem in Artificial intelligence. The question is how to store and manipulate knowledge in an information system in a formal way so that it may be used by mechanisms to accomplish a given task. Examples of applications are expert systems, machine translation systems, computer aided maintenance systems and information retrieval systems (including database front-ends).

Some people think it would be best to represent knowledge in the same way it's represented in human mind, which is the only known working intelligence so far. Other people say that because we don't really know how knowledge is represented in the human mind, any kind of solutions should be tried what is actually done at the moment.

Various notations and artificial languages have been proposed for representing knowledge.

Examples of notations:

• DATR is an example for representing lexical knowledge

Examples of artificial languages intended for knowledge representation include:

• CycL
• Loom

Techniques of knowledge representation

Semantic networks may be used to represent knowledge. Each node represents a concept and the arcs are used to define relations between the concepts.

From earliest times, the knowledge frame[?] or just frame has been used. A frame consists of slots which contain values; for instance, the frame for house might contain a color slot, number of floors slot, etc.

Frames can behave something like object oriented programming languages, with inheritance of features described by the "is-a" link. However, there has been no small amount of inconsistency in the usage of the "is-a" link: Richard P. Gabriel[?] wrote a paper titled "What IS-A is and isn't", wherein 29 different semantics were found in projects whose knowledge representation schemes involved an "is-a" link. Other links include the "has-part" link.

Frames suffer from the Frame problem of knowledge linking.

Scripts are a type of frame that describes what happens temporally; the usual example given is that describing going to a restaurant. The steps include waiting to be seated, receiving a menu, ordering, etc.

First-order predicate calculus may be used as a tool for implementing the above mentioned methods.

See also:

• Metadata
• Ontology
• Douglas Lenat's Cyc project
• Semantic Web

External links:

• What is a Knowledge Representation? (http://medg.lcs.mit.edu/ftp/psz/k-rep) by Randall Davis and others
• DATR Lexical knowledge representation language (http://www.ccl.kuleuven.ac.be/LKR/html/datr)