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Book A.
Introduction

Book B.
7150 Requirements Guidance

Book C.
Topics

Tools,
References, & Terms

SPAN
(NASA Only)

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SWE-121 - Document Alternate Requirements

1. Requirements

6.1.2 Where approved, the requesting Center or project shall document the approved alternate requirement in the procedure controlling the development, acquisition, and/ or deployment of the affected software.

1.1 Notes

NPR 7150.2, NASA Software Engineering Requirements, does not include any notes for this requirement.

1.2 Applicability Across Classes

This requirement applies to all classes and safety criticalities.

Class

  A_SC 

A_NSC

  B_SC 

B_NSC

  C_SC 

C_NSC

  D_SC 

D_NSC

  E_SC 

E_NSC

     F      

     G      

     H      

Applicable?

   

   

   

   

   

   

   

   

   

   

   

   

   

Key:    A_SC = Class A Software, Safety Critical | A_NSC = Class A Software, Not Safety Critical | ... | - Applicable | - Not Applicable
X - Applicable with details, read above for more | P(C) - P(Center), follow center requirements or procedures

2. Rationale

The Center is required to record the alternate requirements obtained through the use of SWE-120 in Center or program/project documentation that controls the development, acquisition, and deployment of the affected software. Publication of the approved alternate requirements helps assure that all affected software engineers are informed of the approved changes. This action will assure the proper implementation of the alternate requirement throughout the various stages of the software life cycle. (See SWE-019 for information on the life cycle process.) The inclusion of these changes in a configuration managed system for the Center or program/project will inform current and future software product developers and project managers of the correct set of requirements and procedures.

3. Guidance

Project personnel record the appropriate information on any requirements changes resulting from the approval of a request made under SWE-120 in the project-specific software requirements documents. This information is placed in the project plan, the software management plan, and the software requirements specification. The Center's compliance matrix to NPR 7150.2 will also include the results of the approval by the Headquarters' Office of the Chief Engineer (OCE). The software team lead will include any updates in the compliance matrix that reflect approved alternate requirements. The software team lead also communicates this information to affected software Technical Authorities (TAs). (See SWE-125 and SWE-128 for information on the content and handling of a compliance matrix.)

When approval is granted for an action from SWE-120, the program/project also includes the results of the request and the rationale for the request, along with any approved alterations to the initial request, in the baselined program/project documentation. Typically, Center changes are reflected in the Center's local implementation of the flowdown of NPR 7150.2, e.g., Center Directives, Center Procedural Requirements covering software engineering, and software assurance plans. The Center-level procedure typically is stored in the Center's central documentation repository. As the alternate requirements generally affect processes, related process assets are updated in the process asset library for future use by software development teams within scope of the generic waiver.

4. Small Projects

Small projects may lack the resources and schedule to individually apply for waiver relief from specific sets of NPR 7150.2 requirements. Centers can request a generic waiver (waived in accordance with SWE-120 and documented under SWE-121) that will cover multiple small projects.

5. Resources

5.1 Tools

Tools to aid in compliance with this SWE, if any, may be found in the Tools Library in the NASA Engineering Network (NEN).

NASA users find this in the Tools Library in the Software Processes Across NASA (SPAN) site of the Software Engineering Community in NEN.

The list is informational only and does not represent an “approved tool list”, nor does it represent an endorsement of any particular tool. The purpose is to provide examples of tools being used across the Agency and to help projects and centers decide what tools to consider.

6. Lessons Learned

A documented lesson from the NASA Lessons Learned database notes the following:

The Pitfalls of "Engineering-by-Presentation" (2005). Lesson Number 1715: Without documenting and, thereby, capturing details of the rationale for decisions affecting systems designs (requirements) "...project staff found themselves repeatedly revisiting the same technical issues. "Now why did we decide..."" This is a good indication that why it was done is as important, at times, as to what was done. OCE (Office of the Chief Engineer) personnel and future projects or Center personnel will be able to avoid reevaluating these general exclusion or alternate requirement approvals if they have appropriate access to the rationale so they can properly understand the basis on which the exclusions were granted in the first place. 566

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