Abstract
Semantic data models comprise formally defined abstractions for representing real world relationships and aspects of the structure of real world phenomena so as to aid database design. While previous research in spatial database design has shown that semantic data models are amenable to explicitly representing some spatial concepts, this paper shows that semantic data models may usefully be applied to the design of spatial databases even without explicitly representing spatial concepts. Specifically, an entity-relationship model comprising only “is-associated-with” relationships is used as the basis from which to define thematic layers for a layer based spatial database.