20. The data processing apparatus of claim 17 , wherein each output port of each stream processing component data structure is modeled using effects of the action associated with the stream processing component.
20. The data processing apparatus of claim 17 , wherein each output port of each stream processing component data structure is modeled using effects of the action associated with the stream processing component. 21. The data processing apparatus of claim 20 , wherein a given stream processing component in the workflow receives a first primal stream at a first input port and wherein the one or more property values for the first primal stream satisfy the one or more preconditions of the first input port.