Exporting and utilizing database interfaces on the web

Database interfaces define the way database functionality is exported to and utilized by end users, developers and programs. Publishing, integration and service-oriented architectures demand capable interfaces and a higher degree of database functionality utilization in order to realize their potential. In service-oriented architectures, applications need to provide integrated access to the data of multiple sources. Such applications typically support only a restricted set of queries over the schema they export, because the participating information sources contribute limited content and limited access methods. In prior work, these limited access methods have often been specified using a set of parameterized views, with the understanding that the integration system accepts only queries which have an equivalent rewriting using the views. These queries are called feasible. Infeasible queries are rejected without an explanatory feedback. To help a developer, who is building an integration application, avoid a frustrating trial-and-error cycle, I introduced the CLIDE query formulation interface, which extends the QBE-like query builder of Microsoft's SQL Server with a coloring scheme that guides the user toward formulating feasible queries. CLIDE provides guarantees that the suggested query edit actions are complete (i.e. each feasible query can be built by following only suggestions), rapidly convergent (the suggestions are tuned to lead to the closest feasible completions of the query) and suitably summarized (at each interaction step, only a minimal number of actions are suggested). In addition, applications need to publish powerful interfaces to end users who query and browse the underlying information sources. Such interfaces require extensive coding and are expensive to maintain. I developed the QURSED system, which semi-automatically generates web- based query form and report pages for semistructured XML data. QURSED drives the generation of the pages from the XML Schema describing the structure of the underlying data and offers to developers an authoring tool that does not require any coding. The resulting forms and reports encode large sets of parameterized queries and are powerful in the sense that heterogeneity, nesting and optionality are tackled declaratively. The system reduces the cost of developing and maintaining web applications by decoupling the query aspects from the visual one