4. The system as recited in claim 3 , wherein when the data separating means separates the stream data based on reusability of the previous query condition evaluation result, the data separating means separates the stream data included in the window evaluation result into duplication input data and new data based on the window definition.
3. The system as recited in claim 2 , wherein the window evaluating means transmits window definition and the window evaluation result to the data separating means when the window evaluation of the stream data is performed.