7.3.3 a Set Theory Model for Anomaly Handling in System Requirements Analysis

Abstract

A mathematical model for system requirements analysis (SRA) is developed utilizing elementary set theory. The model provides a means to explicitly treat unwanted or unexpected conditions that may be experienced by the system being analyzed. The SRA model can also be used to derive completeness criteria for the development of system states, as well as the completeness of the SRA itself. The requirement antecedents (the “under what conditions” for each function and performance requirement) are categorized in accordance with their associated consequences. Although generally applicable, the model finds its highest utility in the area of software requirements because of their unique design processes which focus on system states. As such, a relationship with software development “formal methods” is described.

HAZOP-based identification of events in use cases

“…In order to solve the issue of incomplete exceptions Carson proposed a 3-step approach for requirements elicitation (Carson 1998). The goal of the third step in this approach is to verify requirements completeness, based on the idea of a complementary set of conditions under which the requirements are to be performed (Carson 1995).…”

1.6.4 Requirements Completeness: A Deterministic Approach

“…In keeping with (Carson 1995), this requires that at least one requirement constitute an "or else" condition, such as "|V| > V max ", that extends the parameter over the maximum physical value. This ensures that the analysis of P1 with respect to conditions is complete.…”

“…Following the set theory model of (Carson 1995), the analysis of antecedents is complete so long as the union of parameters is the universal set.…”

Designing for Failure: Anomaly Identification and Treatment in System Requirements Analysis

“…The method complements and extends (Carson 1995) by defining "sufficient" conditions for SRA completeness which complement the previously defined "necessary" conditions for completeness. Identification of the functional failures during the SRA allows the system designer to treat different anomalies rigorously at the beginning of a program as part of the system design.…”

“…The set theory model of (Carson 1995) defines a completeness test for determining whether all possible conditions which may be experienced by a system have an explicit behavior identified in the system requirements analysis (SRA). Because the model defines a "necessary condition" for completeness, however, it can only be applied as a "check" that the analysis is complete.…”