Method for processing stream data and system thereof

A system for processing stream data based on a query, the system comprising:

• a network interface that receives the stream data and a processor that processes the stream data,
• wherein the processor:
• constructs an operator graph comprising information regarding a plurality of operators for processing the stream data based on the query;
• assigns an operator execution order to the plurality of operators based on an inter-operator input and output relation, with respect to all of the operators on the operator graph;
• extracts a set of the operators that maintains the stream data assigned with a time stamp, a time of which is earlier than or equal to a reference time, in an input queue;
• and
• executes processing of the stream data assigned with the time stamp, having the earliest time, in the operator assigned a minimum operator graph execution order among the operators and maintaining the stream data assigned with the time stamp having the earliest time, among the extracted set of the operators.