3a-Requirements Part1 Flashcards
Needs are Requirements
Needs are generally capabilities stated in the language of business management or stakeholders at the business operations levels. Requirements are formal statements that are structured and can be validated—there may be more than one requirement that can be defined for any need.
Generation of requirements
Requirements are generated from needs through a process of requirements analysis (which is also called business analysis or mission analysis at the higher levels).
Levels of needs and requirements
Needs and requirements exist at a number of levels. There is an enterprise view (in which enterprise leadership sets the enterprise strategies and concepts of operations); a business management view (in which business management derive business needs and constraints as well as formalize their requirements); a business operations view (in which stakeholders define their needs and requirements); and a systems view (in which the system is defined in logical and physical views). Subsequently, of course, there are the views at the lower-level of the subsystem and other system elements.
Logical & Physical description
As illustrated here, the enterprise, business management, and business operations views are in the problem domain; the system and subsystem (and lower) views are in the solution domain. As we discussed in earlier modules, the problem domain is generally considered to be the responsibility of those who have ownership of the problem to be solved, so the descriptions of the system are predominantly in the language of the customer’s business management and business operations, focusing on what the system needs to be able to do, how well it should be done, and why—these descriptions are called logical (or often functional) descriptions. On the other hand, the solution domain is generally considered to be the responsibility of those implementing the solution, so the descriptions of the system in that domain are predominantly in engineering and physical terms, focusing on how the problem is to be solved—that is, how it will look once it has been implemented. These latter descriptions are called physical descriptions.
HIGHEST LEVEL
At the highest level, the enterprise has a number of
strategies that will guide its future.
From our perspective, our system has its genesis in
the Concept of Operations (ConOps) which
communicates the leadership’s intentions with
regard to the operation of the organisation—in terms
of existing systems and systems to be developed.
BUSINESS NEEDS AND REQUIREMENTS
The Business Needs and Requirements (BNR) Definition Process begins with the organization’s vision, goals and objectives communicated by the ConOps.
Business management uses this guidance to define Business Needs, largely in the form of Preliminary Life-cycle Concept Documents (PLCD), which capture the Preliminary Acquisition Concept, Preliminary Operational Concept (the Preliminary OpsCon), Preliminary Deployment Concept, Preliminary
Support Concept, and Preliminary Retirement Concept.
life-cycle concepts
- The Operations Concept (OpsCon) describes what the
system will do, how well and why (from the
perspective of the user). - The Acquisition Concept describes the way the
system will be acquired including aspects such as
stakeholder engagement, requirements definition,
solicitation and contracting issues, design,
production, and verification. - The Deployment Concept describes the way the
system will be validated, delivered, and introduced
into operations. - The Support Concept describes the desired support
infrastructure and manpower considerations for
supporting the system after it is deployed. A support
concept addresses operating support, engineering
support, maintenance support, supply support and
training support. - The Retirement Concept describes the way the
system will be removed from operation and retired,
including the disposal of any hazardous materials
used in or resulting from the process.
At this early stage, business management prepare draft, or preliminary concepts, that will be fleshed out late by stakeholders at the business operations level.
Process which transform business needs into requirements
First, however, the Business Needs contained in the Preliminary Life-cycle Concepts are elaborated and formalized into Business Requirements, which are documented in the Business Requirements Specification (BRS), which is also called the Business Requirement Document.
The process by which business needs are transformed into business requirements is called mission analysis or business analysis.
Stakeholder needs and requirements
Once business management are satisfied that their needs and requirements are reasonably complete, they pass them on to the business operations level.
Stakeholder Needs and Requirements (SNR) Definition Process uses the ConOps and the other PLCD as guidance.
Requirements engineers lead stakeholders from the business operations level through a structured process to elicit Stakeholder Needs—in the form of a refined OpsCon document and other Life-cycle Concept Documents (LCD). Stakeholder needs are then transformed into a formal set of Stakeholder Requirements, which are documented in the Stakeholder Requirement Specification (StRS).
That transformation is guided by a formal process of requirements analysis.
SYSTEM LEVEL
At the system level, in the System Requirements Definition Process, the requirements in the StRS are then transformed by requirements engineers into System Requirements, which are documented in the System Requirement Specification (SyRS) (also referred to as the Solution Requirement Specification Document, or simply the System Specification).
Note that the figure illustrates that a number of SyRS may be derived from the StRS. Also note that some organizations may prepare individual LCD for each of a number of systems that are developed to meet the Business Needs. The process then continues for the system elements.
As we observed earlier, the requirements are now physical requirements as they relate to the elements of the system rather than the system itself.
