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A requirement is an expressed demand, desire, expectation, and/or wish to have or not to have a certain marketable and/or a certain capability, condition, feature, and/or property. The plural term, requirements, may refer to the aggregate of various requirements that the product owner or another authority for the requested product and/or its development process has approved, verified, and/or validated. Those requirements that limit the marketable's or process of the production's capabilities and/or conditions are called constraints.


According to the INCOSE Systems Engineering Handbook (4th edition),

Requirement. A statement that identifies a system, product, or process characteristic or constraint, which is unambiguous, clear, unique, consistent, stand‐alone (not grouped), and verifiable, and is deemed necessary for stakeholder acceptability.

Common definitions

The common-style definitions particularly include:

Engineering definitions

According to the Rational Unified Process (RUP), which is an iterative software development process framework that IBM markets,
A requirement describes a condition or capability to which a system must conform; either derived directly from user needs, or stated in a contract, standard, specification, or other formally imposed document.
According to the second version of the A Guide to the Business Analysis Body of Knowledge® (BABOK Guide), a requirement is:
  1. A condition or capability needed by a stakeholder to solve a problem or achieve an objective;
  2. A condition or capability that must be met of possessed by a deliverable or its component to satisfy a contract, standard, specification, or other formally imposed documents; AND/OR
  3. A documented representation of a condition or capability as in (1) or (2).
The IEEE Standard Glossary of Software Engineering Terminology defines a requirement similarly to the two definitions above.

According to the BABOK Guide (3rd edition),

Requirement. A usable representation of a need.

Stakeholder definitions

From a stakeholder perspective, a requirement is anything that helps:
  1. Customers to describe what they wish to obtain;
  2. Suppliers to understand what the customer wants;
  3. Requirements staffers to substantively develop requirements blueprints for their own organizations, as well as other requirements documents such as requirements quality checklists, requirements creator's handbooks, etc.


Requirements are widely used in business analysis, process optimization, procurement, product development, project management, systems engineering, and many other areas. Because of variety of applications, several views of what requirements are, how they should be organized and how they should be utilized compete against each other.

Business analysis

Requirements for the solutions to be designed, developed, and delivered are in the core of business analysis.

New product development

Requirements for the marketables to be designed, developed, and delivered are in the core of new product development. Hewlett-Packard developed the FURPS system, which is quite popular in the software development and particularly promoted by IBM. The Agile methodologies widely use product requirements in forms of user story, epic story, and so on.


Requirements for the marketables to be purchased are in the core of procurement. Forms of the procurement requirements range from oral statements such as I would like to buy the cheapest soap you carry and up to procurement statements of work, business cases, etc.

Project management

Requirements for the unique product, service, or result to be designed, created, and delivered are in the core of project management. AXELOS Ltd and the PMI lead the industry research on requirements.

Sales engineering

Requirements for the products to be sold are in the core of sales engineering. Regardless of the fact whether anyone in marketing and sales knows what the term, requirement, means, any good sales representative asks a potential buyer about what he or she wants to buy at least and, probably, on what conditions and at what price.

Systems engineering

Requirements for the systems to be designed, developed, and delivered are in the core of systems engineering. The IEEE and the INCOSE lead the industry research on requirements.

Natural classifications

Categorized by audiences

Requirements developers develop requirements. There two major pairs of audiences that primarily consume those requirements:
  1. Customer and contractor when the requirements are needed to understand or confirm what needs to be done and, possibly, how what needs to be done would be done.
  2. Contractor's management and implementing staffers when a set of requirements needs to be bettered and/or broken-down in order to be implemented by a contractor's team and/or subcontractors. This type of requirements is often called technical requirements.

Categorized by imposing party

Any requirement can be imposed by one or more of the following three:
  1. Customer, who states what is needed to be solved and, possibly, how what needs to be solved should be solved;
  2. Contractor, who has its own circumstances, both resources and limitations;
  3. Third party such as:
Some requirements are originated from the sources such as demographics, economy, and geography that are outside of those three, but they need to be brought to the operations or project by one of those three.

Categorized by progress

Requirements can be categorized based on their state in the requirement lifecycle:
  1. Stated requirement. A requirement articulated by a stakeholder that has not been analyzed, verified, or validated. Stated requirements frequently reflect the desires of a stakeholder rather than the actual need.
  2. Confirmed requirement.
  3. Prioritized requirement.
  4. Organized requirement.
  5. Modeled requirement.
  6. Verified requirement. Requirements that have been shown to demonstrate the characteristics of requirements quality and as such are cohesive, complete, consistent, correct, feasible, modifiable, unambiguous, and testable.
  7. Validated requirement. A requirement that has been demonstrated to deliver business value and to support the business goals and objectives.
  8. Reviewed requirement.
  9. Approved requirement.
  10. Implemented requirement.

Product vs process

With regard to its nature, a requirement may refer to:

Modeled classifications

Because of the variety of research frameworks, a few competitive taxonomies exist.

IIBA-marketed taxonomy

Particularly through their BABOK Guide, the IIBA markets the following taxonomy:
  1. Business requirement. The highest level of the the IIBA's hierarchy of requirements. Business requirement is a business rationale for one or more changes that, when implemented, will permit the organization to increase revenue, avoid costs, improve service, or meet regulatory requirements. The rationale commonly includes the organizational goals, objectives, and needs; it usually describes opportunities that an organization wants to realize or problems that they want to solve. A business case is the common form of a business requirement.
  2. Stakeholder requirement. Mid-level statements of the needs of a particular stakeholder or group of stakeholders. They usually describe how someone wants to interact with the intended solution. Often acting as a mid-point between the higher-level business requirements and more detailed solution requirements.
  3. Solution requirement, including architecturally significant requirements.
  4. Transition requirement. The lowest level of the the IIBA's hierarchy of requirements. Transition requirements are statements of capabilities or behavior required only to enable the transition from the current state of the enterprise to the desired future state, but that will thereafter no longer be required. Examples include recruitment, role changes, education, migration of data from one system to another.

FURPS+ system

The FURPS+ system for requirements classification has been initially developed by Robert Grady at Hewlett-Packard and is now used widely in the industry, most notably, by IBM. The acronym FURPS represents:
  1. Functionality
  2. Usability
  3. Reliability
  4. Performance
  5. Supportability
The "+" in FURPS+ indicates concerns related to design requirements, implementation requirements, interface requirements, and/or physical requirements.



Those artifacts that serve as requirements can be divided into two categories:
  1. Concept artifacts such as wireframes, mockups, prototypes, etc.
  2. Existing products, especially competitor's ones.

Initiating documents


Main wikipage: Requirements specification
  1. Business requirements document (BRD). Also known as a Business Needs Specification, a BRD is the first stage in a product life cycle. It details the problems that a product/service/system is trying to solve by logically listing high-level business requirements in relation to customers’ needs.
  2. Functional requirements document (FRD). An FRD defines in logical terms, how a system or project will accomplish the requirements laid out in the BRD. It outlines the functionality of the system in detail by capturing the intended behaviour of the system, expressed as services, tasks or functions that the developers have agreed to provide.
  3. Market requirements document (MRD). Sometimes referred to as a Marketing Requirements Document, an MRD focuses on the target market’s needs. It typically explains: What the product is, who the target customers are, what products are in competition with it and why customers are likely to want this product.
  4. Product requirements document (PRD). A PRD is used to communicate everything that must be included in a product release for it to be considered complete. It is written from a user’s point-of-view to understand what a product should do. It usually includes the same content as an FRD, but with ‘non-functional requirements’ added. Although non-functional requirements are not related to the functionality of the product, it’s often important to identify them - they may include such needs as reliability, security and scalability.
  5. Quality requirements document. The quality requirements document outlines the expectations of the customer for the quality of the final product. It consists of various criteria, factors and metrics that must be satisfied.
  6. Software requirements specification (SRS). An SRS outlines the features and the intended behaviour of a system. It describes the business’s understanding of the end user’s needs while laying out functional and nonfunctional requirements.
  7. Technical requirements document (TRD). A TRD contains the software, hardware and platform requirements of the product. It includes requirements like the programming language the system should be developed in and the processor speed required to run the system.
  8. User interface requirements document (UIRD). A UIRD describes the look and feel of the User Interface (UI) of the system.
  9. User requirements document (URD). A requirements document written for a user audience, describing user requirements and the impact of the anticipated changes on the users.

Undocumented requests

Workteam documents

To organize implementation of higher-level requirements, workteams casually use the following lower-level documents:
  • In the Agile methodology:
    1. Product backlog.
    2. Sprint backlog.
    3. Epic story. A large user story that, in its current state, would be difficult to estimate or to complete in a single iteration. Epic stories are typically lower priority and are waiting be broken down into smaller components.
    4. User story. A high-level, informal, brief, non-technical description of a solution capability that provides value to a stakeholder. In other words, a user story is description of a system requirement written from the customer's or end-user's point of view. A user story is typically one or two sentences long and provides the minimum information necessary to allow a developer to estimate the work required to implement it. Either the product owner or the team writes user stories according to the following structure: as a [type of user], I want to [perform some task (or execute some function)], so I can [achieve some goal].
  • In the Waterfall model:
    1. Project task.
    2. Work order.



Main wikipage: Business analysis
Business analysis is the set of enterprise efforts and techniques used to work as a liaison among stakeholders in order to understand the structure, policies and operations of an enterprise, its business needs, and recommend solutions that enable the enterprise to achieve its goals. Use cases are examples of those solutions.


Main wikipage: Requirement lifecycle
A requirement lifecycle is the cycle through which requirements tend to go through from their collection to implementation.

MoSCoW method

The MoSCoW method (alternatively known as MoSCoW analysis, MoSCoW prioritization) is a prioritization technique used in business analysis, enterprise administration, project management, and new product development to reach a common understanding with stakeholders on the importance they place on the delivery of each requirement.
The term, MoSCoW, itself is an acronym derived from the first letter of each of four prioritization categories. Two interstitial Os are added to make the word pronounceable:
  1. Must have. The must-have requirements are critical to the current sprint; missing any of them constitutes a project failure.
  2. Should have. The should-have requirements are important, but not necessary in the current sprint.
  3. Could have. The could-have requirements are desirable but not necessary and can be included if time and other resources permit.
  4. Won't have at this time. The won't-have-this-time requirements are the least-critical, lowest-payback items, or not appropriate in the current sprint.

Responsible staffers

The customers' needs are the origin of the project, so the customer is ultimately responsible for determining their requirement. Governments are responsible for regulations. Other third parties impose expectations, standards, etc. Within the contractor organization, the following staffers are casually involved in developments of requirements, usually the technical ones:
  1. Business analyst. is responsible for discovering the problem/requirements and determining the solution.
  2. Marketing manager. develops the marketing strategy for the project in line with its requirements.
  3. Product manager. is responsible for defining the why, when, and what of the product that the development team will build.
  4. Product owner.
  5. Project manager. is responsible for delivering the solution to a problem.
  6. Systems analyst. uses analysis and design to satisfy business requirements using information technology.
  7. Team lead.

See also

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