The core of the catalogue system is a subdatabase of catalogue information concerning the main items stored in the full database DBMS functionalities. The data stored in the catalogue database includes indices and metadata about the items stored in the main datastore of the library, where the metadata involves abstract textual descriptions of the data and reduced datasets (in particular from the wavelet decomposition.) Since spatially-indexed data comes in many different types and a large variety or representations, it is important to have an appropriate data model for organizing both the data and the metadata.
The component may be viewed in terms of two levels of abstraction: one involving storage organization, indexing schemes, access methods, and support for distributed access to hierarchically structured datasets; the other involving the concepts of conceptual representation for spatial data and metadata, extensibility, basic utilities for common specialized processing needs, and a flexible platform for developing user- or application-specific software tools and interfaces. The problems can be summarized as tasks involving: the development of an appropriate conceptual data organization; the development of a model for metadata organization; the provision of a primitive user interface that includes a set of simple search and browsing operations;, the provision of special tools for image processing that includes operations provided by an locally augmented version of khoros and for text retrieval that is provided by ConQuest; and the provision of a high-level database programming language as a platform for application development. In the remainder of the section, we discuss these problems in detail.