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I struggle with few definitions in knowledge representation and seek credible help to distinguish between them. I have been searching on wikipedia and many websites for the difference between ontologies and semantic networks (not to be confused with semantic web). While the wikipedia page on semantic network never refer to ontologies, they seem extremely similar and have similar application in CS.

My guess is that semantic network are a type of ontology adapted for research on AI. However, I don't know the difference between both. So my question is simply:

Are semantic networks ontologies? If so, are they synonym? or what are the distinctions?

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migrated from Feb 15 '13 at 5:44

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there seems to be very strong notions of type theory in ontologies (ideas of instances, classes, attributes), whereas semantic nets don't seem to carry these. Maybe the distinction is akin to the one between untyped lambda calculus and typed lc? – didierc Feb 15 '13 at 23:34
up vote 9 down vote accepted

A semantic network is a graphic notation for representing knowledge in patterns of interconnected nodes and arcs. It is one way for knowledge visualization and presentation. It was used firstly for for artificial intelligence and machine translation in computer science. What is common to all semantic networks is a declarative graphic representation that can be used either to represent knowledge or to support automated systems for reasoning about knowledge.

Ontology is a representation vocabulary, specialized to some domain or subject. It is a representation of a set of concepts within a domain and the relationships between those concepts. It is used to reason about the properties of that domain, and may be used to define the domain.

You can find more in references as (specially 4):

1) Sowa, John F., ed. “Principles of Semantic Networks: Explorations in the Representation of Knowledge”, Morgan Kaufmann Publishers, San Mateo, CA, 1991.

2) Noy N.F., McGuinnes D. L. “Ontology Development 101: A Guide to Creating Your First Ontology”. Stanford Knowledge Systems Laboratory Technical Report KSL−01−05 and Stanford Medical Informatics Technical Report SMI−2001−0880, March 2001.

3)María Auxilio, “An Overview of Ontologies”, Center for Research in Information and Automation Technologies Technical Report, Interactive and Cooperative Technologies Lab, Universidad De Las Américas Puebla, México, March 2003.

4) ABDEL-BADEEH M. SALEM, MARCO ALFONSE "Ontology versus Semantic Networks for Medical Knowledge Representation", ICCOMP'08 Proceedings of the 12th WSEAS international conference on Computers, 2008.

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Still, it does not completely answer the question. I understand that a semantic network could be use to represent an ontology graphically. No wonder ontology is such a controversial word. – Zonata Feb 19 '13 at 0:30
@Zonata: They are equivalent in some sense. every semantic network could be presented by Ontology and vice Versa. The main diffidence is one is graphical presentation and the other is verbal presentation. – Reza Feb 19 '13 at 0:48

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