Termination properties of spatial Datalog programs

Abstract

We consider spatial databases defined in terms of polynomial Inequalities, and investigate the use of Datalog as a query language for such databases. Recursive programs are not guaranteed to terminate in this setting. Through a series of examples we show that useful restrictions on the databases under consideration or on the syntax of allowed programs, guaranteeing termination, are unlikely to exist. Hence, termination of particular recursive spatial queries must be established by ad-hoc arguments, if it can be established at all. As an illustration of the difficulties that can be encountered in this respect we discuss the topological connectivity query.