ADDING RELATIONAL QUERY FACILITIES TO SOFTWARE-DEVELOPMENT ENVIRONMENTS

Software development environments should include query handlers. Query handlers based on the relational database model are attractive because the model provides a uniform, non-procedural approach to query writing. There are two drawbacks to using the relational model to support query handlers in software development systems: (1) Standard relational database systems require that all information be stored in relations; however, the data structures used by existing software development environments are generally non-relational, and it is impractical to replace them with relations. (2) The standard relational operators are not powerful enough to express certain important classes of queries. We have previously proposed a model of editing environments (Horwitz, Teitelbaum, 1986), based on the use of relationally-attributed grammars, that supports a relational query facility. We introduced a new kind of relation, implicit relations, and a new approach to query evaluation to handle queries that use implicit relations. In this paper we illustrate the utility of implicit relations in contexts other than relationally-attributed grammars. We extend the definition of implicit relations and show how they can be used to support relational query facilities in software development environments without giving up the use of non-relational data structures. Implicit relations can also be used to provide non-standard relational operations such as transitive closure. © 1990.