1. A query processing coordination planning unit˜in a computing system comprising a processor and a memory coupled to the processor, for coordinating a query processing of a user query to obtain requested data from one or more data sources, the query processing coordination planning unit executed by the processor 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 query into a physical representation of the user query, and generating an execution plan expressed by the physical representation of the user query using the one or more query operation providers, wherein each query operation provider in the one or more query operation providers performs a specific operation of the user query and wherein the one or more query operation providers are at least one of a query planner provider, a query transformation provider, or a service provider each of which accept a query framework (QF) query and produce another QF query from the accepted QF query; and a request execution coordinator for executing the physical representation of the user query in accordance with the execution plan using the one or more query operation providers; wherein the request preparation coordinator includes: a conditional operator handler for handling interpretation of conditional elements in the query processing sequence; and a sequence manager for managing invocation of the query operation providers in accordance with the query processing sequence.