A query processing coordination planning unit coordinates a query processing to obtain requested data from one or more data sources. The query processing coordination planning unit comprises a request preparation coordinator and a request execution coordinator. The request planning unit invokes one or more query operation providers in a conditional query processing sequence for translating a logical representation of the user request into a physical representation of a user request, and generates an execution plan expressed by the physical representation of a user request. The request execution coordinator executes the physical representation of the user request in accordance with the execution plan using the query operation providers.