Assessing the Impacts of Uncertainty Propagation to
System Requirements by Evaluating Requirement
Connectivity
Alejandro Salado
Stevens Institute of Technology
Castle Point on Hudson
Hoboken, NJ 07030
asaladod@stevens.edu
Roshanak Nilchiani
Stevens Institute of Technology
Castle Point on Hudson
Hoboken, NJ 07030
rnilchia@stevens.edu
Copyright © 2013 by Alejandro Salado and Roshanak Nilchiani. Published and used by INCOSE with permission.
Abstract. Although theoretically independent, requirements within a decomposition level of a
system architecture are not isolated elements. For an existing design, a change of a requirement
may endanger or facilitate fulfillment of other requirements within the same level of the
decomposition. The present research suggests a requirement connectivity metric to evaluate the
potential consequences that changing a requirement may have on a system with respect to
fulfillment of other requirements. A particular aspect of the present research is the assumption
that connectivity accounts only for requirements within the same decomposition level of an
architecture, not for those flowing up or down the decomposition. The metric is used to
evaluate different cases in which requirements are changed due to triggering of uncertain
events during a project life-cycle.
Introduction
It is widely recognized that various types of change during a development process often
negatively affect cost, schedule, and quality. Consequently, the study of how change
propagates along the elements composing a system that is under development is becoming an
important topic of research in different engineering disciplines and industries. For example,
(Hassan and Holt 2004) address the importance of predicting change in software systems and
provide some heuristics for its management. Heuristics are also proposed in the field of product
development (Keller, Eckert, and Clarkson 2006), where the majority of research has focused
attention to the impacts on physical components derived from changes on other physical
components. (Clarkson, Simons, and Eckert 2001) and (Oduncuoglu and Thomson 2011)
include risk as a measure on the prediction of change propagation of product development. In a
research spanning several years and over 41,500 change requests in a number of industry cases
(Giffin et al. 2009) provide some metrics to quantitatively evaluate the effect of change
propagation and find out that the majority of change requests occur during system integration
and test.
Changes can however occur or be a result of changes in elements or artifacts surrounding the
system under development, apart from the elements of the system under study. (Koh and
Clarkson 2009) explore this idea and incorporate other elements in the evaluation of change
propagation during product development, namely design features and requirements (which in
systems engineering jargon can be interpreted as stakeholder requirements and system
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