The National Cancer Institute has developed the NCI Thesaurus, a biomedical vocabulary for cancer research, covering terminology across a wide range of cancer research domains. A major design goal of the NCI Thesaurus is to facilitate translational research. We describe: the features of Ontylog, a description logic used to build NCI Thesaurus; our methodology for enhancing the terminology through collaboration between ontologists and domain experts, and for addressing certain real world challenges arising in modeling the Thesaurus; and finally, we describe the conversion of NCI Thesaurus from Ontylog into Web Ontology Language Lite. Ontylog has proven well suited for constructing big biomedical vocabularies. We have capitalized on the Ontylog constructs Kind and Role in the collaboration process described in this paper to facilitate communication between ontologists and domain experts. The artifacts and processes developed by NCI for collaboration may be useful in other biomedical terminology development efforts.

A knowledge-base management system (KBMS) with the following goals is proposed: (1) to allow a knowledge engineer to update a knowledge base and have these updates persist on secondary storage, (2) to allow multiple knowledge engineers to have shared access to a knowledge base and modify the knowledge base concurrently, and (3) to maintain consistency of the shared knowledge base as it evolves. At the heart of the KBMS is the version store, which is a persistent storage structure that maintains multiple versions of a knowledge base. Retrieve and update operations are defined on the version store to efficiently access and modify any version. Objects in the version store are clustered to support efficient access of an entire version or some subparts of it. To store the effects of an update requires space proportional to the size of the update and which is independent of the size of the knowledge base. The additional cost of maintaining multiple versions is within a small constant factor of maintaining a single version.>