The purpose of Requirements Development (RD) is to produce and analyze customer, product, and product component requirements.

This process area describes three types of requirements: customer requirements, product requirements, and product component requirements. Taken together, these requirements address the needs of relevant stakeholders, including those pertinent to various product lifecycle phases (e.g., acceptance testing criteria) and product attributes (e.g., safety, reliability, and maintainability). Requirements also address constraints caused by the selection of design solutions (e.g., integration of commercial off-the-shelf products).

All development projects have requirements. In the case of a project that is focused on maintenance activities, the changes to the product or product components are based on changes to the existing requirements, design, or implementation. The requirements changes, if any, might be documented in change requests from the customer or users, or they might take the form of new requirements received from the requirements development process. Regardless of their source or form, the maintenance activities that are driven by changes to requirements are managed accordingly.

Requirements are the basis for design. The development of requirements includes the following activities:

·   Elicitation, analysis, validation, and communication of customer needs, expectations, and constraints to obtain customer requirements that constitute an understanding of what will satisfy stakeholders

·   Collection and coordination of stakeholder needs

·   Development of the lifecycle requirements of the product

·   Establishment of the customer requirements

·   Establishment of initial product and product component requirements consistent with customer requirements

This process area addresses all customer requirements rather than only product-level requirements because the customer may also provide specific design requirements.

Customer requirements are further refined into product and product component requirements. In addition to customer requirements, product and product component requirements are derived from the selected design solutions. Throughout the process areas, where we use the terms product and product component, their intended meanings also encompass services and their components.

Requirements are identified and refined throughout the phases of the product lifecycle. Design decisions, subsequent corrective actions, and feedback during each phase of the product’s lifecycle are analyzed for impact on derived and allocated requirements.

The Requirements Development process area includes three specific goals. The Develop Customer Requirements specific goal addresses defining a set of customer requirements to use in the development of product requirements. The Develop Product Requirements specific goal addresses defining a set of product or product component requirements to use in the design of products and product components. The Analyze and Validate Requirements specific goal addresses the necessary analysis of customer, product, and product component requirements to define, derive, and understand the requirements. The specific practices of the third specific goal are intended to assist the specific practices in the first two specific goals. The processes associated with the Requirements Development process area and those associated with the Technical Solution process area may interact recursively with one another.

Analyses are used to understand, define, and select the requirements at all levels from competing alternatives. These analyses include the following:

·   Analysis of needs and requirements for each product lifecycle phase, including needs of relevant stakeholders, the operational environment, and factors that reflect overall customer and end-user expectations and satisfaction, such as safety, security, and affordability

·   Development of an operational concept

·   Definition of the required functionality

The definition of functionality, also referred to as “functional analysis,” is not the same as structured analysis in software development and does not presume a functionally oriented software design. In object-oriented software design, it relates to defining what are called “services” or “methods.” The definition of functions, their logical groupings, and their association with requirements is referred to as a “functional architecture.”

Analyses occur recursively at successively more detailed layers of a product’s architecture until sufficient detail is available to enable detailed design, acquisition, and testing of the product to proceed. As a result of the analysis of requirements and the operational concept (including functionality, support, maintenance, and disposal), the manufacturing or production concept produces more derived requirements, including consideration of the following:

·   Constraints of various types

·   Technological limitations

·   Cost and cost drivers

·   Time constraints and schedule drivers

·   Risks

·   Consideration of issues implied but not explicitly stated by the customer or end user

·   Factors introduced by the developer’s unique business considerations, regulations, and laws

A hierarchy of logical entities (functions and subfunctions, object classes and subclasses) is established through iteration with the evolving operational concept. Requirements are refined, derived, and allocated to these logical entities. Requirements and logical entities are allocated to products, product components, people, or associated processes.

Involvement of relevant stakeholders in both requirements development and analysis gives them visibility into the evolution of requirements. This activity continually assures them that the requirements are being properly defined.

Refer to the Requirements Management process area for more information about managing customer and product requirements, obtaining agreement with the requirements provider, obtaining commitments with those implementing the requirements, and maintaining traceability.

Refer to the Technical Solution process area for more information about how the outputs of the requirements development processes are used, and the development of alternative solutions and designs used in refining and deriving requirements.

Refer to the Product Integration process area for more information about interface requirements and interface management.

Refer to the Verification process area for more information about verifying that the resulting product meets the requirements.

Refer to the Validation process area for more information about how the product built will be validated against the customer needs.

Refer to the Risk Management process area for more information about identifying and managing risks that are related to requirements.

Refer to the Configuration Management process area for information about ensuring that key work products are controlled and managed.

Specific Goal and Practice Summary

SG 1 Develop Customer Requirements

SP 1.1       Elicit Needs

SP 1.2       Develop the Customer Requirements

SG 2 Develop Product Requirements

SP 2.1       Establish Product and Product Component Requirements

SP 2.2       Allocate Product Component Requirements

SP 2.3       Identify Interface Requirements

SG 3 Analyze and Validate Requirements

SP 3.1       Establish Operational Concepts and Scenarios

SP 3.2       Establish a Definition of Required Functionality

SP 3.3       Analyze Requirements

SP 3.4       Analyze Requirements to Achieve Balance

SP 3.5       Validate Requirements