A CONCEPTUAL DESIGN OF A SOIL DATABASE FOR A GEOGRAPHICAL INFORMATION-SYSTEM

Soil maps and soil descriptions can be combined with other data sets w ithin a geographical information system, to be used for analysis and m odelling. As the amount of data to be included in such a database and the number of users of the database increase, the need for a structure d approach to database design arises. In this paper, we discuss the co nceptual design of a geographical database of soil information. We use an Extended Entity-Relationship (EER) model to capture the semantics and constraints of the database. The EER schema is then mapped into th e relational data model. We show how the Structured Query Language (SQ L) can be used to formulate sample queries that may be of interest to users of such a soil database. We also illustrate uses of the EER mode l in graphical formulation of database queries. Because of its high le vel of abstraction and intuitive simplicity, the EER model constitutes a convenient tool for both database design and formulation of databas e queries.