Important issues relate to the set of organizing principles for a library's collection that are supported by a library and the ways of making such multi-organizations interoperable between libraries. A second and related enhancement involves the great variety of metadata that it is possible to extract, store, and retrieve about items and the various organizations that may be imposed on a library's collections using such metadata. Such distinctions are very important in the case of multimedia libraries. Items such as images and maps, for example, have huge numbers of interpretations concerning their content, and require significant extensions of traditional cataloging practices in order to characterize them in a manner that is useful for user access and browsing. Critical issues that arise concern the classes of metadata to be extracted from library items of different types and the procedures for extracting such metadata.
Ontologies provide the basis for the many indexing schemes that are possible.
Ontologies may be multiple, overlapping, hierarchically organized, and amenable to object-oriented representations. Important issues concern the construction and use of various ontologies and the interoperability of libraries with respect to such ontologies. Important general issues concern the role of the librarian in constructing the extended metadata and catalogs that are required, as well as issues relating to standards and protocols for metadata extraction, organization, and access. A few of the research problems relating to the issues identified above include Standards and protocols concerning metadata in its widest sense. Metadata and catalog support for multimedia items, and their special attributes, such as lineage and multiple concrete representations.