We define collection-level metadata (CLM) as information about the contents of a collection. The term collection has a range of meanings (Hill et al., 1999), but here is defined simply as a group of objects accessible through a common catalog, such that the existence of a given item of information in the collection can be determined unambiguously. Both the objects and the catalog might be stored on a single server; or the catalog might exist on one server, and point to objects on many servers