1. A method of assigning sampling methods to each input stream for arbitrary query sets in a data stream management system, the method comprising: splitting all query nodes in a query directed acyclic graph (DAG) having multiple parent nodes into sets of independent nodes having a single parent node; and generating via a processor a final grouping set based on a reconciliation between the multiple child nodes that share a parent node for at least one node describing how to sample an input stream for the at least one node.