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Engineering > Spec Guidelines



A document intended primarily for use in procurement, which clearly and accurately describes the essential technical requirements for items, materials, or services including the procedures by which it will be determined that the requirements have been met.


Systems Engineering Guidebook, James N. Martin, CRC Press, pg. 211


Relationship between SOW and Specifications.  The SOW defines (either directly or by reference to other documents) all work (non-specification) performance requirements for contractor effort.  Technical design and performance requirements are contained in specifications.  Such specifications are typically referenced in the SOW, but specific technical requirements should not be spelled out in the SOW.  Together, the specification and SOW provide what a contractor needs to know in order to prepare a proposal or bid in response to a Request for Proposals (RFP).  The contract references and supplements the specification and statement of work.



Choosing the Type of Specification.  Simple guidelines are provided below to assist in choosing the appropriate type of specification.  Format guidelines are also provided.

Development Specifications.

A document which states performance, interface, and other technical requirements in sufficient detail to permit design, engineering for service use, and evaluation.

The General Requirements Document (GRD) and System Requirements Documents (SRDs which are the tier of specifications immediately below the GRD) are development specifications.  Lower tier development specifications may also be generated.  Development specification should be maintained current during production when it is desired to retain a complete statement of performance requirements.  Format guidelines for development specs are provided here.


Product Specifications

A document applicable to a production item below the system level which states item characteristics in a manner suitable for procurement, production, and acceptance.

Product specifications are oriented toward procurement or fabrication of a product through specification of primarily performance requirements or detail design requirements.

Performance Specifications. A performance specification is used for for procuring a component by specifying its functionality - the supplier does the design.  It states requirements in terms of the required results and provides criteria for verifying compliance, but it does not state methods for achieving results.  It defines the functional requirements for the product, the environment in which it must operate, and the interface and interchangeability requirements. 


Detail Specifications. A detail specification is used for procuring or fabricating a component by specifying its design - the project does the design.  It specifies design requirements such as materials to be used, how a requirement is to be achieved, or how an item is to fabricated or constructed. 

Performance and detail specifications use a common 6-section format (7-sections including appendices).

Format guidelines for product specs are provided here.


A comparison of the content for performance and detail specifications is provided here.


Product Requirements Lists.   Product requirements lists (PRLs) are used for purchasing commercially available items.  PRLs should describe, by functional or performance characteristics, the available, acceptable commercial products that will satisfy the Project's needs.  The format of the PRL is at the discretion of the originator.  However, PRLs must be referenceable documents, signed, and subject to revision control. 

Specification Do's and Dont's

  • Specifications should include all and only those requirements needed to establish suitability for the intended purpose.  Requirements be so written that compliance with all requirements will assure the suitability of the item for its intended purpose, and non-compliance with any requirement will indicate unsuitability for the intended purpose. Only requirements that are necessary and practicably attainable should be specified.

  • Requirements should be quantitative rather than qualitative.  The specification must ensure that parties submitting proposals or bids - and those evaluating them - are equally clear on exactly what the requirements are. Requirements that are not based on quantitative data are subject to varying interpretations and misunderstanding. 

  • Requirements should be verifiable. The project must be able to determine through analysis, inspection, or test if a product will perform as required. Verifiable requirements also assist the manufacturer. By specifying how a requirement will be verified, the manufacturer has a clearer idea of what is required.

  • Specifications should exclude unnecessary information.  Use the "What if I left this out?" criterion.

Style Instructions.  Specifications should be prepared in the same style as other controlled documents.

Style instructions for document preparation are provided here.

A sample specification is provided here.

NCSX v. PPPL Spec Guidelines.  PPPL has a procedure for preparation, review, and approval of specifications and statements of work (ENG-006).  Differences are summarized below.

  • NCSX guidelines provide a clear distinctions between what belongs in a spec and what belongs in a SOW.  ENG-006 does not.  There is overlap in the ENG-006 guidelines for specifications and SOWS  For instance,  ENG-006 guidelines for Section 4 - Test and Inspection Requirements are identical for specifications and SOWs.  Non-technical requirements such as QA Program requirements, documentation requirements, and deliverables are strictly in SOWs per the NCSX guidelines whereas they can appear in both documents in ENG-006.

  • NCSX guidelines require a correspondence between requirements in Section 3 and how it will be determined that those requirements have been met in Section 4.  ENG-006 does not mandate verification of the requirements in the specification.

  • ENG-006 provides useful content guidance.  NCSX personnel are encouraged refer to ENG-006 in considering what requirements should be applied to the contractor effort.  However, NCSX format guidelines should be followed for determining whether those requirements belong in a specification or SOW.

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