Evaluation methods in SARA—the graph model simulator

Abstract

The supported methodology evolving in the SARA (System ARchitects' Apprentice) system creates a design frame-work on which increasingly powerful analytical tools are to be grafted. Control flow analyses and program verification tools have shown promise. However, in the realm of the complex systems which interest us there is a great deal of research and development to be done before we can count on the use of such powerful tools. We must always be prepared to resort to experiments for evaluation of proposed designs. This paper describes a fundamental SARA tool, the graph model simulator. During top-down refinement of a design, the simulator is used to test consistency between the levels of abstraction. During composition, known building blocks are linked together and the composite graph model is tested relative to the lowest top-down model. Design of test environments is integrated with the multilevel design process. The SARA methodology is exemplified through design of a higher level building block to do a simple FFT.

SARA (System ARchitects Apprentice): Modeling, analysis, and simulation support for design of concurrent systems

“…There is no guaranteed equivalence between the various models in the spectrum. As demonstrated in [27], one may have to rely on experiments to increase confidence that two useful models of the same system do not disagree. Regardless of the model-equivalence problems, the flexibility offered to the designer is important.…”

“…The decision to explicitly model the environment of a system being designed led to invention of a test environment [27] to accompany every level of system specification and every building block model intended for use in composition of systems. Simulation with a test environment validates model behavior over selected test cases, and encourages the design of testable systems.…”

“…In practice, explicit modeling of a test environment of- fers a foundation for design of testable systems [27]. It is natural to design and model test conditions which will determine satisfaction of requirements at the same time at which the system is being modeled.…”

An experimental distributed modeling system

“…Information Control Nets are graph models of data and control flow in offices; they bear similarities to several other graph models used in computer system modeling, for example, those developed by Razouk, Vernon, and Estrin [32]. An ICN is composed of a set of activities and a set of repositories.…”