A semantic network is often used as a form of knowledge representation. It is a directed graph consisting of vertices which represent concepts and edges which represent semantic relations between the concepts.
Semantic networks are a common type of machine-readable dictionaries.
Important semantic relations:
- Meronymy (A is part of B)
- Holonymy (B has A as a part of itself)
- Hyponymy (or Troponymy) (A is subordinate of B; A is kind of B)
- Hyperonymy (A is superordinate of B)
- Synonymy (A denotes the same as B)
- Antonymy (A denotes the opposite of B)
The link and lexical structure of the Wikipedia might also be regarded as a simple example of a semantic network, with the following properties:
- article A is linked to article B
- the name of article A is used in the Wikipedia entry for B
"Semantic Nets" were first invented for computers by Richard H. Richens of the Cambridge Language Research Unit in 1956 as an "interlingua" for machine translation of natural languages. They were developed as "semantic networks" for knowledge representation and reasoning by M. Ross Quillian in 1966.
On can consider a mind map to be a very free form variant of a semantic network. By using colors and pictures the emphasis is on generating a semantic net which evokes human creativity.
In the 1960s to 1980s the idea of a semantic link was developed within hypertext systems as the most basic unit, or edge, in an semantic network. These ideas were extremely influential, and there have been many attempts to add typed link semantics to HTML and XML.