Types of databases commonly used for handling taxonomic data are compared. It is shown that none of the existing types of databases fully support the requirements of taxonomic data. The results of this comparison provide a rationale for the design and implementation of a new database system based on an Extended Object-Oriented model. The new model, the Prometheus Object-Oriented Model (POOM) and its query language Prometheus Object-Oriented Language (POOL), are discussed in relation to the requirements of taxonomic data and the Prometheus Taxonomic Data Model. POOM provides the ability to represent the semantics of relationships between data. This allows us to build the type of graph structures that are found in taxonomic hierarchies. In ad...