A Hierarchical Graph Model of Concurrent Real-Time Software Systems

Author:Stotts, Paul, Department of Computer ScienceUniversity of Virginia

A model of a software system is introduced which is based on the theory of H - graph semantics. The model is intended to support a variety of performance studies for realtime concurrent programs. This work presents the formal concepts of the model, and discusses some analyses that can be applied to it. The model of a concurrent system includes not only the application program but the host hardware as well, viewed as a collection of procedures with duration but no structure. Each procedure model in the system has three components: a data model. a static program model. and a control flow model. Concurrency is represented in the control flow component by a marked, timed Petri net which is distinguished by its notion of place duration and its restricted firing rule. A technique using Parallel Flow Graphs is introduced for producing well structured Petri nets with obvious interpretations in terms of software. With such models. we can automatically detect and correct conflicts in accesses to shared variables and data structures. as well as produce upper and lower bounds on execution times for portions of the modeled system. The analyses use a modified form of the Petri net reachability tree, one in which the effects of the concurrent firing rule and token timing are represented as restricting the set of reachable states.
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Source Citation:

Stotts, Paul. "A Hierarchical Graph Model of Concurrent Real-Time Software Systems." University of Virginia Dept. of Computer Science Tech Report (1986).

University of Virginia, Department of Computer Science
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