Aucs/tr9507 Database Object Creation Subject to Constraint Rules Using a Constraint Logic Search Engine

The P/FDM object database is based on a semantic data model in which stored data is integrated with derived data which is computed by Prolog rules retrieved from the class de-scriptors stored in the database. These rules may also be inherited. They are generated from declarative deenitions expressed in the functional data language Daplex. Other Prolog rules are generated from integrity constraints expressed as invariant Daplex expressions, and these rules are triggered by relevant updates, and used to check semantic integrity. We are interested in using complex updates as part of design work. Thus, we do not execute update actions immediately following failure of a triggered rule, since these may in turn trigger other failures and knock-on actions, giving rise to anomalous rule behaviour. Instead we ask a constraint solver to nd a set of values which consistently satisfy all the constraints. This set of values is then committed as a single update action. This paper describes how information from constraints (both semantic and structural) is compiled into constraint logic form for the CHIP constraint solver, and how information on the generated objects is fed back. The system is implemented and has re-used signiicant parts of the Daplex query language parser and optimiser.