1. A query processing coordination planning unit for coordinating a query processing of a user request to obtain requested data from one or more data sources, the query processing coordination planning unit comprising: a request preparation coordinator for invoking one or more query operation providers in a conditional query processing sequence to translate a logical representation of the user request into a physical representation of a user request, and generating an execution plan expressed by the physical representation of a user request; and a request execution coordinator for executing the physical representation of the user request in accordance with the execution plan using the query operation providers.