1. A computer program product for processing a stream of tuples, each tuple containing one or more attributes, the computer program product comprising a computer readable storage medium having program code embodied therewith, the program code comprising computer readable program code configured to: process the attributes of the stream of tuples using stream operators operating on one or more computer processors and corresponding one or more processing elements; process, with a first processing method, a group of tuples from the stream of tuples into a grouping window, wherein the first processing method is configured to: identify a membership condition, determine whether the membership condition is met by a tuple from the stream of tuples, evict the tuple from the grouping window in response to the membership condition being unmet, and include the tuple in the grouping window in response to the membership condition being met; and process, with a second processing method, a subgroup of tuples from the group of tuples into a subgrouping window, wherein the second processing method is configured to: identify a sub-membership condition, determine whether the sub-membership condition is met by a tuple from the group of tuples, wherein the membership condition and the sub-membership condition are not the same condition type, and include the tuple in the subgrouping window in response to the sub-membership condition being met.