A visual interface and navigator for the P/FDM object database

Abstract

We have implemented a Java-based visual interface for P/FDM which has at its centre a graphical representation of the database schema. Users construct queries by clicking on entity classes and relationships in the schema diagram and constraining the values of attributes selected from menus. As this is done, the Daplex text of the query under construction is built up in a subwindow (the query editor window). Queries are submitted to the database via a CORBA interface. Results satisfying the selection criteria are displayed in a table in a separate result window, together with the Daplex text of the query. A particularly novel feature of the interface is a "copy-and-drop" facility which enables the user to select and copy data values in the result window and then "drop" these into the query editor window. When this is done, the selected values are merged into the original query automatically, in the appropriate place in the query text, to produce a more specialised query. This query can then be extended by the user, if required, and submitted to the database for execution. Thus, complex queries can be built up in stages by inspecting intermediate results and modifying the follow-on queries to have stronger selection criteria and additional navigation links.