On the Definition of Terms in a Requirements Expression

Abstract

The purpose of a requirement expression is to communicate clearly the needs of various entities into a formal language such that the intent is clearly understood by all involved: those whose job it is to implement the requirement, those responsible for proving the built system meets the requirement, and those responsible for proving the resulting system meets the needs of the relevant entity. Although many sources provide definitions of the terms associated with a requirement expression, there are only occasional agreements on common definitions, and the defined terms are too narrowly focused to be useful across the full requirements engineering domain. This paper proposes a cohesive set of definitions of the terms associated with a requirement expression. First, a framework for the transformation of needs into requirements is briefly discussed and existing definitions are presented from major relevant sources. These definitions are then analyzed and a cohesive set of definitions is offered for the key terms associated with a requirements expression: entity; need; requirement statement; and the requirement attributes that, along with the requirement statement itself, comprise the requirement expressions in a requirement set.

Issues in Capturing and Utilizing Non-Functional Requirements along the Road to Servitization

“…Looking at the relationship between needs and requirements, Ryan et al (2015) define the distinction to be that needs are the tacit explanation of the desired state in a natural form while requirements are the explicit and formal description of this state. The target of requirement elicitation is then to, as clearly as possible, translate the naturally expressed needs to formal requirements without introducing biases (Gomez Sotelo et al, 2018).…”

Obsolescence, rarefaction and their propagation

“…A system must meet customer needs and expectations. "A need is the result of a formal transformation of one or more concepts into an agreed-to expectation for an entity to perform some function or possess some quality (within specified constraints)" (INCOSE 2015) and (Ryan et al 2015). "Requirements define what a system is supposed to do, i.e.…”

“…they are specifications of services that the system should provide, or constraints or circumstances under which the system is required to operate" (Dahlstedt 2001). "A requirement statement is the result of a formal transformation of one or more needs into an agreed-to obligation for an entity to perform some function or possess some quality (within specified constraints)", (Ryan et al 2015). (ISO/ IEC/IEEE:29148 2011) proposes a detailed classification of requirements which are: functional, performance, modes/ states, interface, operational, usability, design, physical, adaptability, environmental conditions, policies/regulations, cost/schedule constraints, and logical.…”

TORUS: Tracing Complex Requirements for Large Cyber-Physical Systems

“…Estimating completeness and other metrics can be complex and time-consuming, yet they are crucial in order to successfully deliver a product that meets the expectations of all of its stakeholders (M. J. Ryan, Wheatcraft, Dick & Zinni, 2015).…”