Interactive query formulation over web service-accessed sources

Integration systems typically support only a restricted set of queries over the schema they export. The reason is that 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, we introduce 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. We provide 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 needed to preserve completeness are suggested). We present the algorithms, implementation and performance evaluation showing that CLIDE is a viable on-line tool.