Optimizing aggregates over correlated windows in a stream-query system

Methods, systems, apparatuses, and computer program products are provided for determining a query plan. A query is received that comprises a request for a data result for each of a plurality of original time windows. The plurality of original time windows included in the query are identified. An initial window representation is generated that identifies a set of connections between windows in a window set that includes at least the original time windows. A revised window representation is generated that includes an alternative set of connections between windows in the window set based at least on an execution cost for at least one window. The revised window representation is selected to obtain the data result for each of the plurality of original time windows. A revised query plan based on the revised window representation is provided to obtain the data result for each of the plurality of original time windows.