Requirements analysis

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A systems engineering perspective on requirements analysis. SE Process.jpg
A systems engineering perspective on requirements analysis.

In systems engineering and software engineering, requirements analysis focuses on the tasks that determine the needs or conditions to meet the new or altered product or project, taking account of the possibly conflicting requirements of the various stakeholders, analyzing, documenting, validating and managing software or system requirements. [2]

Contents

Requirements analysis is critical to the success or failure of a systems or software project. [3] The requirements should be documented, actionable, measurable, testable, [4] traceable, [4] related to identified business needs or opportunities, and defined to a level of detail sufficient for system design.

Overview

Conceptually, requirements analysis includes three types of activities:[ citation needed ]

Requirements analysis can be a long and tiring process during which many delicate psychological skills are involved. New systems change the environment and relationships between people, so it is important to identify all the stakeholders, take into account all their needs and ensure they understand the implications of the new systems. Analysts can employ several techniques to elicit the requirements from the customer. These may include the development of scenarios (represented as user stories in agile methods), the identification of use cases, the use of workplace observation or ethnography, holding interviews, or focus groups (more aptly named in this context as requirements workshops, or requirements review sessions) and creating requirements lists. Prototyping may be used to develop an example system that can be demonstrated to stakeholders. Where necessary, the analyst will employ a combination of these methods to establish the exact requirements of the stakeholders, so that a system that meets the business needs is produced.[ citation needed ] Requirements quality can be improved through these and other methods

Requirements analysis topics

Stakeholder identification

See Stakeholder analysis for a discussion of people or organizations (legal entities such as companies, standards bodies) that have a valid interest in the system. They may be affected by it either directly or indirectly. A major new emphasis in the 1990s was a focus on the identification of stakeholders. It is increasingly recognized that stakeholders are not limited to the organization employing the analyst. Other stakeholders will include:

Joint Requirements Development (JRD) Sessions

Requirements often have cross-functional implications that are unknown to individual stakeholders and often missed or incompletely defined during stakeholder interviews. These cross-functional implications can be elicited by conducting JRD sessions in a controlled environment, facilitated by a trained facilitator (Business Analyst), wherein stakeholders participate in discussions to elicit requirements, analyze their details and uncover cross-functional implications. A dedicated scribe should be present to document the discussion, freeing up the Business Analyst to lead the discussion in a direction that generates appropriate requirements which meet the session objective.

JRD Sessions are analogous to Joint Application Design Sessions. In the former, the sessions elicit requirements that guide design, whereas the latter elicit the specific design features to be implemented in satisfaction of elicited requirements.

Contract-style requirement lists

One traditional way of documenting requirements has been contract style requirement lists. In a complex system such requirements lists can run to hundreds of pages long.

An appropriate metaphor would be an extremely long shopping list. Such lists are very much out of favour in modern analysis; as they have proved spectacularly unsuccessful at achieving their aims[ citation needed ]; but they are still seen to this day.

Strengths

  • Provides a checklist of requirements.
  • Provide a contract between the project sponsor(s) and developers.
  • For a large system can provide a high level description from which lower-level requirements can be derived.

Weaknesses

  • Such lists can run to hundreds of pages. They are not intended to serve as a reader-friendly description of the desired application.
  • Such requirements lists abstract all the requirements and so there is little context. The Business Analyst may include context for requirements in accompanying design documentation.
    • This abstraction is not intended to describe how the requirements fit or work together.
    • The list may not reflect relationships and dependencies between requirements. While a list does make it easy to prioritize each individual item, removing one item out of context can render an entire use case or business requirement useless.
    • The list does not supplant the need to review requirements carefully with stakeholders in order to gain a better shared understanding of the implications for the design of the desired system / application.
  • Simply creating a list does not guarantee its completeness. The Business Analyst must make a good faith effort to discover and collect a substantially comprehensive list, and rely on stakeholders to point out missing requirements.
  • These lists can create a false sense of mutual understanding between the stakeholders and developers; Business Analysts are critical to the translation process.
  • It is almost impossible to uncover all the functional requirements before the process of development and testing begins. If these lists are treated as an immutable contract, then requirements that emerge in the Development process may generate a controversial change request.

Alternative to requirement lists

As an alternative to requirement lists, Agile Software Development uses User stories to suggest requirements in everyday language.

Measurable goals

Best practices take the composed list of requirements merely as clues and repeatedly ask "why?" until the actual business purposes are discovered. Stakeholders and developers can then devise tests to measure what level of each goal has been achieved thus far. Such goals change more slowly than the long list of specific but unmeasured requirements. Once a small set of critical, measured goals has been established, rapid prototyping and short iterative development phases may proceed to deliver actual stakeholder value long before the project is half over.

Prototypes

A prototype is a computer program that exhibits a part of the properties of another computer program, allowing users to visualize an application that has not yet been constructed. A popular form of prototype is a mockup, which helps future users and other stakeholders to get an idea of what the system will look like. Prototypes make it easier to make design decisions, because aspects of the application can be seen and shared before the application is built. Major improvements in communication between users and developers were often seen with the introduction of prototypes. Early views of applications led to fewer changes later and hence reduced overall costs considerably. [ citation needed ]

Prototypes can be flat diagrams (often referred to as wireframes) or working applications using synthesized functionality. Wireframes are made in a variety of graphic design documents, and often remove all color from the design (i.e. use a greyscale color palette) in instances where the final software is expected to have graphic design applied to it. This helps to prevent confusion as to whether the prototype represents the final visual look and feel of the application. [ citation needed ]

Use cases

A use case is a structure for documenting the functional requirements for a system, usually involving software, whether that is new or being changed. Each use case provides a set of scenarios that convey how the system should interact with a human user or another system, to achieve a specific business goal. Use cases typically avoid technical jargon, preferring instead the language of the end-user or domain expert . Use cases are often co-authored by requirements engineers and stakeholders.

Use cases are deceptively simple tools for describing the behavior of software or systems. A use case contains a textual description of the ways in which users are intended to work with the software or system. Use cases should not describe internal workings of the system, nor should they explain how that system will be implemented. Instead, they show the steps needed to perform a task without sequential assumptions.

Requirements specification

Requirements specification is the synthesis of discovery findings regarding current state business needs and the assessment of these needs to determine, and specify, what is required to meet the needs within the solution scope in focus. Discovery, analysis and specification move the understanding from a current as-is state to a future to-be state. Requirements specification can cover the full breadth and depth of the future state to be realized, or it could target specific gaps to fill, such as priority software system bugs to fix and enhancements to make. Given that any large business process almost always employs software and data systems and technology, requirements specification is often associated with software system builds, purchases, cloud computing strategies, embedded software in products or devices, or other technologies. The broader definition of requirements specification includes or focuses on any solution strategy or component, such as training, documentation guides, personnel, marketing strategies, equipment, supplies, etc.

Types of requirements

Requirements are categorized in several ways. The following are common categorizations of requirements that relate to technical management: [1]

Business requirements

Statements of business level goals, without reference to detailed functionality. These are usually high-level (software and/or hardware) capabilities that are needed to achieve a business outcome.

Customer requirements

Statements of fact and assumptions that define the expectations of the system in terms of mission objectives, environment, constraints, and measures of effectiveness and suitability (MOE/MOS). The customers are those that perform the eight primary functions of systems engineering, with special emphasis on the operator as the key customer. Operational requirements will define the basic need and, at a minimum, answer the questions posed in the following listing: [1]

Architectural requirements

Architectural requirements explain what has to be done by identifying the necessary systems architecture of a system.

Structural requirements

Structural requirements explain what has to be done by identifying the necessary structure of a system.

Behavioral requirements

Behavioral requirements explain what has to be done by identifying the necessary behavior of a system.

Functional requirements

Functional requirements explain what has to be done by identifying the necessary task, action or activity that must be accomplished. Functional requirements analysis will be used as the toplevel functions for functional analysis. [1]

Non-functional requirements

Non-functional requirements are requirements that specify criteria that can be used to judge the operation of a system, rather than specific behaviors.

Performance requirements

The extent to which a mission or function must be executed; generally measured in terms of quantity, quality, coverage, timeliness or readiness. During requirements analysis, performance (how well does it have to be done) requirements will be interactively developed across all identified functions based on system life cycle factors; and characterized in terms of the degree of certainty in their estimate, the degree of criticality to system success, and their relationship to other requirements. [1]

Design requirements

The "build to", "code to", and "buy to" requirements for products and "how to execute" requirements for processes expressed in technical data packages and technical manuals. [1]

Derived requirements

Requirements that are implied or transformed from higher-level requirement. For example, a requirement for long range or high speed may result in a design requirement for low weight. [1]

Allocated requirements

A requirement that is established by dividing or otherwise allocating a high-level requirement into multiple lower-level requirements. Example: A 100-pound item that consists of two subsystems might result in weight requirements of 70 pounds and 30 pounds for the two lower-level items. [1]

Well-known requirements categorization models include FURPS and FURPS+, developed at Hewlett-Packard.

Requirements analysis issues

Stakeholder issues

Steve McConnell, in his book Rapid Development, details a number of ways users can inhibit requirements gathering:

This may lead to the situation where user requirements keep changing even when system or product development has been started.

Engineer/developer issues

Possible problems caused by engineers and developers during requirements analysis are:

Attempted solutions

One attempted solution to communications problems has been to employ specialists in business or system analysis.

Techniques introduced in the 1990s like prototyping, Unified Modeling Language (UML), use cases, and agile software development are also intended as solutions to problems encountered with previous methods.

Also, a new class of application simulation or application definition tools have entered the market. These tools are designed to bridge the communication gap between business users and the IT organization — and also to allow applications to be 'test marketed' before any code is produced. The best of these tools offer:

See also

Related Research Articles

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  1. A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful.
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In product development and process optimization, a requirement is a singular documented physical or functional need that a particular design, product or process aims to satisfy. It is commonly used in a formal sense in engineering design, including for example in systems engineering, software engineering, or enterprise engineering. It is a broad concept that could speak to any necessary function, attribute, capability, characteristic, or quality of a system for it to have value and utility to a customer, organization, internal user, or other stakeholder. Requirements can come with different levels of specificity; for example, a requirement specification or requirement "spec" refers to an explicit, highly objective/clear requirement to be satisfied by a material, design, product, or service.

<span class="mw-page-title-main">Systems development life cycle</span> Systems engineering terms

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In software project management, software testing, and software engineering, verification and validation (V&V) is the process of checking that a software system meets specifications and requirements so that it fulfills its intended purpose. It may also be referred to as software quality control. It is normally the responsibility of software testers as part of the software development lifecycle. In simple terms, software verification is: "Assuming we should build X, does our software achieve its goals without any bugs or gaps?" On the other hand, software validation is: "Was X what we should have built? Does X meet the high-level requirements?"

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Requirements management is the process of documenting, analyzing, tracing, prioritizing and agreeing on requirements and then controlling change and communicating to relevant stakeholders. It is a continuous process throughout a project. A requirement is a capability to which a project outcome should conform.

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<span class="mw-page-title-main">Functional specification</span>

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In requirements engineering, requirements elicitation is the practice of researching and discovering the requirements of a system from users, customers, and other stakeholders. The practice is also sometimes referred to as "requirement gathering".

<span class="mw-page-title-main">Misuse case</span>

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Software requirements for a system are the description of what the system should do, the service or services that it provides and the constraints on its operation. The IEEE Standard Glossary of Software Engineering Terminology defines a requirement as:

  1. A condition or capability needed by a user to solve a problem or achieve an objective
  2. A condition or capability that must be met or possessed by a system or system component to satisfy a contract, standard, specification, or other formally imposed document
  3. A documented representation of a condition or capability as in 1 or 2

In software engineering, a software development process or software development life cycle (SDLC) is a process of planning and managing software development. It typically involves dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design and/or product management. The methodology may include the pre-definition of specific deliverables and artifacts that are created and completed by a project team to develop or maintain an application.

Business requirements, also known as stakeholder requirements specifications (StRS), describe the characteristics of a proposed system from the viewpoint of the system's end user like a CONOPS. Products, systems, software, and processes are ways of how to deliver, satisfy, or meet business requirements. Consequently, business requirements are often discussed in the context of developing or procuring software or other systems.

References

  1. 1 2 3 4 5 6 7 8 Systems Engineering Fundamentals Archived 2011-07-22 at the Wayback Machine Defense Acquisition University Press, 2001
  2. Kotonya, Gerald; Sommerville, Ian (1998). Requirements Engineering: Processes and Techniques . Chichester, UK: John Wiley and Sons. ISBN   9780471972082.
  3. Alain Abran; James W. Moore; Pierre Bourque; Robert Dupuis, eds. (March 2005). "Chapter 2: Software Requirements". Guide to the software engineering body of knowledge (2004 ed.). Los Alamitos, CA: IEEE Computer Society Press. ISBN   0-7695-2330-7 . Retrieved 2007-02-08. It is widely acknowledged within the software industry that software engineering projects are critically vulnerable when these activities are performed poorly.
  4. 1 2 Project Management Institute 2015, p. 158, §6.3.2.

[1]

Bibliography

  1. Anderson, Charlotte (2022-06-08). "Why You Need Stakeholder Identification and Analysis | Acorn". Acorn PLMS. Retrieved 2024-01-19.