Clarity regarding controlled vocabularies, taxonomies, thesauri, ontologies, and metamodels. With all the scuttlebut going around about folksonomies and tagging, these are important terms to understand. In the process of tagging, it's pretty noticeable
G. Angelova. Proceedings of the 13th International Conference on Conceptual Structures (ICCS 2005), Volume 3596 von Lecture Notes in Computer Science, Seite 367-380. Springer, (2005)