Product modelling using multiple levels of abstraction: instances as types

Most databases make use of three levels of abstraction, namely: the data dictionary, the database schema and the database contents. The data dictionary describes the structure of the database schema whilst the database schema describes the structure of the database contents. This approach fits perfectly in situations with large quantities of "simple" data and relatively small and stable structures. In this paper, we will focus on "product models" which cannot be modelled easily with these levels of abstraction. We will illustrate the modelling problem with an example and present a solution using the Leeds Product Data Editor.