Evaluation of Functionality in Distributed Systems
MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INFORMATION AND DECISION SYSTEMS
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A new quantitative methodology is presented for identifying and evaluating the shortfalls and the overlaps between the desired functionality of a distributed decision making system, as characterized by the design requirements, and the functionality of a proposed or implemented distributed system. First, compatible Petri Net models of both the requirements and the system are presented. Second, a correspondence is established between structural properties of the Petri Net representation of the system and the functions it performs. On the performance side, a functionality is defined as a set of coordinated functions that a system must be able to carry out in order to accomplish a task. On the structural side, simple and complete information flow paths, i.e., sub-nets of a Petri Net, are defined. Thus a particular functionality is identified as a sub-net of the Petri Net representation of the system. Algorithms are presented to determine the various simple and complete information flow paths in the nets representing both the system and the requirements. This is accomplished through extensive use of the invariant theory of Petri Nets. The next step is the comparison of the two sets of flow paths to determine shortfall and overlaps. The formulation of the problem requires a set of definitions that characterize the shortfalls and the overlaps in a precise manner. The methodology is illustrated by applying it to a hypothetical command center.
- Command, Control and Communications Systems