Applying Heuristics to Model the System Physical Architecture How can systems engineering better incorporate nonfunctional requirements into their design and development activities? By José L. Fernández and Juan A. Martínez Copyright © 2021 by José L. Fernández and Juan A. Martínez. All rights reserved. Authored for PPI SyEN.
Abstract: One of the challenges that systems engineers must face is how to meet nonfunctional requirements when they develop the model of the system physical architecture. Unfortunately, some of the most common MBSE (Model-Based Systems Engineering) methodologies do not provide specific guidance to implement nonfunctional requirements. In this article, we apply the MBSE methodology, ISE&PPOOA (Integrated Systems Engineering & Pipelines of Processes in Object Oriented Architectures) [1] to model the physical architecture of an intravascular medical device, where quality attributes such as safety, resilience, and other “-ilities” (reliability and maintainability) are important. Introduction
best practice to implement those nonfunctional requirements that are driven by connectivity and architecture. Accordingly, heuristics and trade-off are complementary best practices promoted by ISE&PPOOA methodology [1].
ISE&PPOOA MBSE methodology promotes three best practices to deal with requirements that are complementary and can be applied iteratively during the system-architecture modeling process. The first best practice is allocation, where “functional + performance” requirements are allocated to the system components, taking into consideration maximum-cohesion and minimum-coupling principles. The application of this produces what is called the modular architecture in ISE&PPOOA (Figure 1). But functional allocation does not address nonfunctional requirements, for which two additional best practices are proposed: tradeoff assessment, and the use of heuristics. We use trade-off to select the best technology for implementing the system core components, based upon attributes that include the ability of those components to accommodate relevant nonfunctional requirements [2]. However, some of those requirements affect not just the selection of components but also their connections that form the architecture of the system. Therefore, heuristics are the proposed 20
Figure 1. From modular to refined architecture using ISE&PPOOA
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