Methods and systems of processing a data stream are disclosed. A developer may develop a service only by programming a Service Unit (SU) including a service logic (SL) and including a Service Unit Description Language (SUDL) file, so that the developer may not need to program complicated stream processing code, such as stream source connection code, network input/output (I/O) code, and buffering code. In addition, the stream source connected dynamically to the service and a service execution mode (such as push and pull modes) may be converted by simply changing setting files based on the service model. The system includes modules for managing and processing the stream in reality, such as stream source connection modules, network I/O processing modules, and stream buffering modules, the modules operating the developed program through the service model.