Dynamic and structured presentation of database contents on the Web

Attractive presentation of database contents is a key component of Web-based businesses. TFE (Target Form Expression) is a database publishing/presentation extension of SQL that yields a query result presented as a document in any of several target media, for example, HTML, Java, LaTeX. When a Web (HTML) document is the target medium, TFE yields intra-page and inter-page hierarchical structures in arbitrary size and complexity. The inter-page structures are automatically-generated hyper-links which allow the resulting Web document to be browsed in a fashion similar to drill down in a data warehouse. In this paper, we introduce a new primitive of TFE that allows the invocation of another query. Combined with the incremental evaluation of invoked queries, it improves both efficiency and functionality compared to monolithic and static implementations. The improved functionality includes recursive navigation. A small number of query rewriting rules are provided to show the equivalence of a query and its decompositions. Incremental query evaluation gives application system an enhanced capability for designing database/Web applications to meet performance and functionality requirements while retaining simplicity of description. A new diagramming method called Database Presentation Diagram is also introduced to visualize the structures of a set of queries and the presentation produced with them.