 Recently, work on ontological categories has attracted interest not only among philosophers, but also in information science and the biomedical sciences, where ontologies are used to organize the knowledge represented in information systems (Smith 2003). In some cases, the ontologies developed are domain-specific (e.g. specific to medical information, geographic information, etc.), but there has also been a great deal of interest in developing a ‘top-level’ ontology of maximally general categories applicable to all specific domains and enabling data sharing across systems. It is such top-level ontologies that draw upon philosophical work on ontological categories most directly, although categorial distinctions also play a crucial role in domain-specific ontologies. Both sorts of philosophical work on categorization promise to have a wide variety of practical applications to information management that are just beginning to be explored (see Sowa 1995, Munn &amp; Smith (eds.) 2008)