User defined topological predicates in database systems
Current database systems cannot only store standard data li ke integer , string , and real values, but also spatial data like points , lines , and regions . The importance of topological relationships between spati al objects has been recognized a long time ago. Using the well known 9 inters ection model for describing such relationships, a lot of constella tions can be distinguished. For the query language of a database system it is not desirabl e to have such a large number of topological predicates. Particularl y the query lan- guage should not be extended by a large number of topological predicates. This paper describes how a database system user can define and use her own topological relationships. We show algorithms for comp uting user defined topological predicates in an efficient way. Last, we co mpare these general versions with specialized implementations of topo logical predi- cates.
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