User defined topological predicates in database systems

Current database systems cannot only store standard data like integer\underline{integer}, string\underline{string}, and real\underline{real} values, but also spatial data like points\underline{points}, lines\underline{lines}, and regions\underline{regions}. The importance of topological relationships between spatial objects has been recognized a long time ago. Using the well known 9-intersection model for describing such relationships, a lot of different topological relationships can be distinguished. For the query language of a database system it is not desirable to have such a large number of topological predicates. Particularly the query language should not be extended by a lot of predicate names. It is desirable to build new relationships from existing ones, for example to coarse the granularity. This paper describes how a database system user can define and use her own topological predicates. We show algorithms for computing such predicates in an efficient way. Last, we compare these general versions with specialized implementations of topological predicates.