| Summary: | The linear data manipulation languages (DMLs) used to query typical relational databases have a number of practical disadvantages for users of all levels. The aim of graphical query languages is to provide efficiency for the expert and ease of use for the novice, without losing the power of a traditional DML. GQL provides a graphical query interface for relational databases. Queries are expressed graphically and translated into a DML before being passed to the host database for execution. The graphical interface of the Macintosh is used to provide facilities for incremental editing of queries as well as the display of results. A local dictionary is used to store metadata, which may be extracted from the host database or defined within GQL, for use in query formulation. Predefined relationships (or "join recipes") may be used to construct linkage conditions in queries. Parametrized subqueries may be stored for reuse, enabling both the provision of "black box" query components for use by novices and the maintenance of libraries of frequently-used components by experts.
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