A logical data model for integrated geographical databases

An approach to the design and the development of geographical database systems based on the integration of different specialized databases is investigated. This approach is supported by an extension of the relational model which makes it possible to separate interaction issues from integration issues, guaranteeing independence between the logical level and the physical level. The introduced extended logical model guarantees to the user a uniform and expressive view of geographical entities, while making it possible to refer to them and access them through both descriptive and geometrical/spatial characteristics. On the other hand, the logical model gives the designer a formal methodology and formal framework for the correct specification of the geographical information at the logical level