Purpose - The paper explores the basics of semiotic analysis and concept theory that represents two dominant approaches to knowledge representation, and explores how these approaches are fruitful for knowledge organization.

Design/methodology/approach - In particular the semiotic theory formulated by the American philosopher C.S. Peirce and the concept theory formulated by Ingetraut Dahlberg is investigated. The objective of this paper is to compare the differences and similarities between these two theories of knowledge representation.

Findings - The semiotic model is a general and unrestricted model of signs and Dahlberg’s model is thought from the perspective and demand of better KOS development. We find that Dahlberg’s concept model provides us with a detailed method for analyzing and representing concepts in a KOS, where semiotics provides the philosophical context for representation.

Originality/value - This paper is the first paper that combines theories of knowledge representation, semiotic and concept theory, within the context of knowledge organization.