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4.1. Introduction, Definition and Purpose of Stakeholder Requirements

Introduction - The starting point of engineering a system is the definition of the problem to be solved. The stakeholders’ requirements represent the view of the users, acquirers, and customers of the problem. An important set of activities has to be performed to establish a set of stakeholders’ requirements for a system that can provide the services needed by the acquirer, the users, and the other stakeholders in a defined environment. This section provides knowledge about the notions of needs, expectations, stakeholders’ requirements, concept of operations, and the related systems engineering activities and methods. The set of Stakeholder Requirements represents one of the major outcomes of these activities. For better understanding of this chapter, it is recommended that you read sections 3.3.3.1 and 3.3.3.2 first.

Definition and Purpose - An initial presentation of stakeholders’ intention is not necessarily a requirement, since it has not been defined, analyzed, or determined to be feasible. This intention is distinguished from a requirement as being (stakeholder) needs, goals or objectives. The distinction between requirements and needs is related to which system is concerned; for example, a requirement for a system may be allocated to a software element of the system, viewed as needs by the supplier of this software element, and further elaborated as (a) requirement(s) for this software element.

An important aspect of engineering is “requirements engineering.” Some activities gathered under this term include:

  • the capture of the needs, goals, and objectives of the various stakeholders;
  • the preliminary identification of the engineering elements of this system-of-interest in terms of purpose, expected mission, services or operations, objectives, exchanges, and physical links with the objects of its context of use;
  • the enrichment of the needs through the analysis of these first engineering elements of the system, in particular what is called the “mission analysis”;
  • the transformation of these needs into clear, concise, and verifiable Stakeholders’ Requirements applicable to the system-of-interest;
  • the analysis and translation of the Stakeholders’ Requirements into a set of System Requirements (see section 3.3.5).

Requirements engineering is performed in an iterative manner with the other life cycle processes and recursively through the system design hierarchy.

4.2. Principles about Stakeholder Requirements

4.2.1. From capture of needs to the Stakeholders’ Requirements definition

Several steps are necessary to state the maturity of the needs, from "real needs" to reaching a realized solution (that could be called "realized needs"). Figure 4 presents the “Cycle of Needs” as it can be deduced from Professor Shoji Shiba and Professor Noriaki Kano's works and courses, and is adapted here for systems engineering purposes.

FIGURE 4

This figure shows these steps and the position of the Stakeholder Requirements and System Requirements in the engineering cycle:

  1. Real needs are those that lie behind any perception, and indeed may not be perceived at all; they are conditioned by the context in which people live. As an example, a generic need could be “identify infectious diseases easily”. It often looks like a simple action.
  2. Perceived needs are based on a person’s awareness (possibly imperfect) that something is wrong, that there is a lack of something, or that there is something that could improve a situation. Perceived needs are often presented as a list of disorganized expectations, often resulting from an analysis of the usage conditions for the considered action. Following on from the example above, the real need might be perceived as a need to "carry out medical tests in particular circumstances (laboratories, point of care, hospital, human dispensary)". Since the real need is seldom expressed, the richness of the knowledge of the perceived needs is used as a basis for potential solutions. This step has to be as complete as possible to cover all the contexts of use.
  3. Expressed needs originate from perceived needs in the form of generic actions or constraints, and are typically prioritized. For example, if safety is the top concern, the expressed need “Protect the operator against contamination” may take priority over other expressed needs, such as “Assist in the execution of tests.” Here the analysis of the expected mission or services in terms of operational scenarios takes place.
  4. Retained needs use the prioritization of expressed needs in order to achieve something or make solutions feasible. The retained needs allow the consideration of potential solutions. The retained needs are generally called "Stakeholder Requirements,” and exploration of potential solutions must start from this step. The various solutions suggested at this step are not yet products but describe means of satisfying the Stakeholder Requirements. Each potential solution imposes constraints on the future system-of-interest.
  5. Specified needs, generally called “System Requirements”, are the translation of the stakeholders’ requirements to represent the view and expression of the supplier of the problem. The expression of the System Requirements means that potential solutions exist or can be developed, manufactured, or bought.
  6. Realized needs are the system, product, or service realized, taking into account every System Requirement (and hence Stakeholder Requirement).

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4.2.2. Mission Analysis and Operational Concept

The notion of Mission Analysis and of Concept of Operations originated from Defense organizations to define the tasks and actions performed within a context of military operations, taking into account the strategic, operational, and tactical aspects of a given situation.

  • The mission analysis is the process used to identify all unit missions and critical collective tasks. Collective tasks must be identified to determine exactly what the unit must be trained in to support accomplishment of unit missions. ((TRADOC 1999, Appendix A), specifically references for AR 25-30, The Army Integrated Publishing and Printing Program; FM 25-100, Training the Force; FM 25-101, Battle Focused Training; and FM 100-23, Peace Operations. Etc.)
  • The concept of operations is a clear, concise statement of where, when, and how the commander intends to concentrate combat power to accomplish the mission. It broadly outlines considerations necessary for developing a scheme of maneuver. (U.S. Army 1997, 1-268)

These notions are also used in industrial sectors as aviation administrations and aeronautic transportation, health care systems, Space, etc. with adapted definitions and/or terms, such as operational concepts. Examples include:

  • “Mission Analysis” is the term used to describe the mathematical analysis of satellite orbits, performed to determine how best to achieve the objectives of a space mission (European Space Agency).
  • In a large-scale system, such as chemical and nuclear plants, the system functional requirement changes during its operation and its component must also play various roles depending on the system state. Since the logical relation between the system and its components changes during system operation, the phased mission analysis (PMA) must be introduced into their reliability analysis (Kohda, Wada, and Inoue 1994, 299-309).

Anywhere these notions are used, it is evident that they are based on fundamental concepts such as operational mode (or operational state of the system), scenario (of actions), operational concepts, functions (provided services), etc. In other words, the system encounters different states during its utilization or operation (operational modes). During each state scenarios of services are performed (operational concept); therefore, a scenario is a sequence of actions, functions or services. This means that during the Stakeholder Requirements definition, the description of operational scenarios is a powerful means to identify the expected or required services of the future system. On the other hand, if the expected services are (pre) defined, the expression of operational scenarios provides the expected behavior of the system in use; that is to say, how the user intends to use the system in its various operational modes.

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4.2.3. Classification of Stakeholder Requirements

Several classifications of stakeholder requirements are possible, e.g., (ISO/IEC June 2010, section 9.4.2.3). These classifications of Stakeholder Requirements have the goal to facilitate the classification of the system requirements and, subsequently, to prepare the design and validation activities. One possible way to classify the stakeholder requirements is under the following categories:

  1. Service or functional: sets of actions to perform the mission or operations of the system-of-interest; enhanced by effectiveness or performance characteristics attached to the mission or operations
  2. Operational: states and transitions between states of the system-of-interest during its utilization to include dynamic interactions between the system-of-interest (viewed as a black box) and the system-of-interest’s interface with external components in the context of its use
  3. Interface: matter, energy, or information flows exchanged between the system-of-interest and its external components in the context of its use, including physical links
  4. Environmental: external conditions affecting the system when in operation
  5. Utilization characteristics: the ‘-ilities’ used to indicate conditions of the utilization of the system-of-interest (e.g. usability, dependability, security, etc.)
  6. Human factors: capabilities of users and operators, ergonomics
  7. Logistical: acquisition, transportation, and storage of elements needed by the system-of-interest to perform its services
  8. Design constraints: re-use of existing components or forbidden materials, for example
  9. Further categories as necessary.

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