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
A. Plangprasopchok, K. Lerman, and L. Getoor. Proceedings of the 16th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, page 949--958. New York, NY, USA, ACM, (2010)
V. Zacharias, and S. Braun. Workshop on Social and Collaborative Construction of Structured Knowledge (CKC), 16th International World Wide Web Conference (WWW 2007), (8-12 May 2007)