Investigation of Algebraic Query Optimisation for Database Programming Languages

A major challenge still facing the designers and implementors of database programming languages (DBPLs) is that of query optimisation. We investigate algebraic query optimisation techniques for DBPLs in the context of a purely declarative functional language that supports sets as first-class objects. Since the language is computationally complete issues such as non-termination of expressions and construction of infinite data structures can be investigated, whilst its declarative nature allows the issue of side effects to be avoided and a richer set of equivalences to be developed. The support of a set bulk data type enables much prior work on the optimisation of relational languages to be utilised. Finally, the language has a well-defined semantics which permits us to reason formally about the prop erties of expressions, such as their equivalence with other expressions and their termination.