Systems Engineering

System Requirements Document (SRD)

The System Requirement Document (SRD) defines system-level functional and performance requirements for a system. The SRD is derived from the Capability Development Document (CDD), Concept of Operations (CONOPS), system-level performance metrics, mission threads/use cases, and usage environment and is developed by the program office.  It should include a system-level description of all software elements required by the preferred system concept.

Definition: The Systems Requirements Document (SRD) translates warfighter Capability Based Requirements into performance based acquisition requirements for a system or subsystem in any program milestone or phase.

When is the System Requirements Document (SRD) Developed

The SRD is developed during the Technology Maturation & Risk Reduction (TMRR) Phase, but a draft SRD should be developed for the Analysis of Alternatives (AoA) in the Materiel Solutions Analysis (MSA) Phase. The program office uses the SRD to provide more detailed requirements than what’s provided in the CDD and is normally included in a solicitation package. The SRD should be finalized before the contract award. [1]

System Requirements Document (SRD) Development

The SRD should be developed with feedback and input from the industrial base. Once the SRD is placed on contract, the contractor will further develop the specification and develop their own, more detailed requirements document and System Specifications; sometimes called a Weapons Systems Specification (WSS).

Definition of System Specification: A type of program-unique specification that describes the requirements and verification of the requirements for a combination of elements that must function together to produce the capabilities required to fulfill a mission need, including hardware, equipment, software, or any combination thereof. [2]

Steps in Developing a System Requirements Document (SRD)

The steps in developing an SRD are the same as those for any other requirements document.

  • Follow Requirements Development Steps
  • Follow MIL-STD-961E “Defense and Program-Unique Specifications Format and Content” when developing the SRD.
  • A contractor may build an internal document to manage their requirements’ traceability. If they call this an SRD, you might want to call yours a system specification to avoid confusing the two. Any requirements in their document should be ultimately traceable back to your system performance specification.
  • The SRD and WSS should all be traceable to the Initial Capabilities Document (ICD) and CDD.
Figure: Requirements Development Steps

 

System Requirements Document Notionial (SRD) Outline

Below is a notional outline of the SRD derived from the template. For more details, download the template.

  1. Scope: This paragraph contains a full identification of the system or subsystem and associated software to which this document applies, including, as applicable, identification number(s), title(s), abbreviation(s), and release number(s) where known.
  2. Applicable Document: This section lists the number, title, revision, and date of all documents referenced herein. This section also identifies the source for documents unavailable through normal Government stocking activities.
  3. Requirements: This section identifies the basic system or subsystem requirements the warfighter needs.
  4. Verification Provisions: This section defines a set of verification methods and specifies for each requirement in section 3 the method(s) to be used to ensure the requirement has been met.
  5. Requirements Traceability: For a system-level SRD, this paragraph includes traceability requirements to a warfighter Capability Document and down to applicable subsystems.
  6. Appendix

Software Requirements Specification (SRS)

The term “System Requirements Document” is a phrase commonly used to describe a “Software Requirements Specification.” If your acquisition is exclusively for software, you may call yours a “Software Requirements Specification” or “System Requirements Document”.

Definition of Software Requirements Specification (SRS): A software requirements specification is a document that describes what the software will do and how it will be expected to perform. It also describes the functionality the product needs to fulfill all stakeholder’s needs.

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Updated: 2/18/2024

Rank: G3.3

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