Abstract. The annotation of the GENIA corpus, a set of biomedical articles, targets the classification of biological entities based on their association with a domain-tailored taxonomy of categories. By incorporating information extraction process on the corpus we have developed a knowledge base (KB) that includes a more comprehensive taxonomy of categories, relationships between biological entities, and a hierarchy of relationships. We present our experiences in exploring the expressiveness of OWL to accommodate our KB. OWL proves to be sufficient to accommodate the extracted knowledge, however, it lacks expressive power when generalization of knowledge is needed. To this end we endorse recent endeavors in extending OWL with fuzzy description logic. 1