In this paper we will construct and investigate various aspects of a new, formal model for database structures. In particular we will concentrate on providing a general model for database schemas which will be basically functional ([HK87]), and will support specialization relationships. Wherever possible we try to minimize the number of different concepts involved in modelling both schemas and database instances, in order to get as simple and uniform a model as possible. We construct a representation of databases instances which supports object identity, and define what it means for an instance to satisfy a database schema. Despite its simplicity, our model is very general and expressive, so that database schemas and instances arising from a number of other data models can be translated into the model.