K. Siorpaes and M. Hepp, myOntology: The Marriage of Collective Intelligence and Ontology Engineering, in Proceedings of the Workshop Bridging the Gap between Semantic Web and Web 2.0 at the ESWC 2007. LNCS Springer: Innsbruck, Austria, June 7, 2007.
Gruber said he saw four different ways of adding meta-tags to material, ranging from the loosest to the most strict:
1.Folksonomy (informal, user-defined)
2.Controlled vocabularies (the user must deploy a set of defined terms)
3.Taxonomy (Pre-defined terms in which specific terms are subsets of more general terms)
4.Ontology (A rich set of relationships is mapped out among all the terms)
A. Plangprasopchok, K. Lerman, und L. Getoor. Proceedings of the 16th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, Seite 949--958. New York, NY, USA, ACM, (2010)