Petri-net-based modeling and evaluation of pipelined processing of concurrent database queries

A description is given of a Petri-net-based methodology for modeling and evaluation of pipelined processing of concurrent database queries in an integrated data network (IDN). An extended Petri-net model is presented and used to model two key approaches to concurrent database query processing in the IDN, namely, pipelined and data-flow-based execution of queries and intermediate data sharing among concurrent queries. Database operations are categorized, and the models for the data flow and control flow in them are presented. A general-purpose Petri-net simulator has been developed using event-driven programming techniques and used to simulate the execution of the Petri-net models of some test queries. The results validate the results of a previous analytical evaluation in which the advantages of pipeline and intermediate data sharing were established. Since all the essential details of query processing in the IDN have been simulated, the results of this simulation study are believed to present closely the workings of the actual system