In general, there seems little point in trying to define terms for use except within some closely knit community of practice. Nevertheless, glossaries are often interesting attempts to clarify the conceptual context of activities. This is the case with the RDN discussion of structured and unstructured services, brokers and portals, and so on. Another interesting example has just appeared from the Reusable Learning initiative of NSDL: the Reusable Learning Glossary. This defines terms in relation to its Granularity, Interoperability and Layers Matrix, a welcome attempt to make some distinctions between what it calls content assets, information objects, learning objects, learning components, and learning environments.