Logical Optimisation of Distributed Knowledge Base Queries
Malcolm C. Taylor · The Computer Journal · 1990
Query optimisation is a crucial element in providing acceptable performance in a distributed knowledge base system. This paper considers optimisation in a heterogeneous environment where each node provides an interface to a common model. The common model is object-oriented, using unnormalised relations with an extended relational algebra as query language. Both the data structures and the language are formally defined using the Vienna Development Method (VDM). These formal definitions are then used as a basis for deriving conditions under which various optimising transformations can be applied.