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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-120 - General Exclusion from Requirements

1. Requirements

6.1.1 For those cases in which a Center or project desires a general exclusion from requirement(s) in this NPR or desires to generically apply specific alternate requirements that do not meet or exceed the requirements of this NPR, the requester shall submit a waiver for those exclusions or alternate requirements for approval by the NASA Headquarters' Chief Engineer with appropriate justification.

1.1 Notes

This type of waiver (which is approved by the NASA Headquarters' Chief Engineer) is for generic/blanket relief from a requirement for a Center, Center organization, or multiple projects over an extended time. Generic/blanket waivers are not to be confused with normal waivers that address relief from a requirement on a single project or in a specific instance (which can be approved at the Center level if so specified in last column of Appendix D [of NPR 7150.2]).

1.2 Applicability Across Classes

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

Centers and multi-Center projects typically create local directives and processes that address Agency-wide requirements as well as additional requirements from lessons learned from software anomalies and failures on similar systems. This requirement is intended to eliminate the need for repetitive waivers across similar projects at a Center or across multiple Centers in the case of a major project.  Generic waivers of this nature are needed for Agency requirements relief in Center Procedural Requirements documentation as well as high-level documents on major programs/projects.  

The issuance of generic waiver coverage provides a Center's programs/projects relief from specific requirements within the specified scope for current and future software engineering activities, until the waiver's expiration date.  

The distinctive characteristic of this requirement is the allowance of waivers that span multiple projects at a given Center, as well as allowing major programs and projects to be granted waivers across multiple elements.

3. Guidance

The scope and duration of the requested generic waiver are especially important considerations. NPRs and Center Directives are typically updated in 5-year cycles, making this a reasonable upper limit for waiver duration in this situation. The program's/project's life cycle can range from less than a year to 30+ years within NASA's environment. While it may be tempting to make the duration of a waiver last until project retirement, this approach is strongly discouraged for long-duration projects. The scope of generic waivers is closely scrutinized by the NASA Headquarters' Chief Engineer, as unintended risks to current and future projects are difficult to analyze. NASA has well documented classifications for project categories and priority levels (NPR 7120.5, NASA Space Flight Program and Project Management Requirements 082; NPR 7120.7, NASA Information Technology and Institutional Infrastructure Program and Project Management Requirements 264; and NPR 7120.8, NASA Research and Technology Program and Project Management Requirements 269), payload categories (NPR 8705.4, Risk Classification for NASA Payloads 048), and software classification and whether it is Safety Critical (NPR 7150.2 and NASA-STD-8739.8, NASA Software Assurance Standard 278). It is recommended that the scope of generic waivers be stated in well-understood terms and categories.

Risk is always one of the primary considerations in evaluating a waiver for approval by a NASA Technical Authority (TA). Requesters are to ensure that risks are well documented with sound rationale in the waiver request. In some instances, alternative techniques can mitigate these risks. The mitigating factors are documented so the TA can clearly understand the resulting risk being accepted by the Center or program/project. This Handbook has a section on related NASA Lessons Learned for many NPR 7150.2 requirements.  These Lessons Learned provide a good start to identifying risk related to projects not performing specific requirements. 

The second type of generic waiver addresses the replacement of specific with alternative requirements by the Center or program/project. Advanced software technology and/or tools may mitigate risks associated with not implementing a set of NPR 7150.2 requirements but may fail to meet the requirement itself. Alternative Center-specific requirements might be proposed as a replacement to one or more requirements in the NPR. The likelihood that the waiver will be approved lessens if the alternate requirements set negatively changes the projects' risk profile unnecessarily, reduces safety, or impacts quality.

While on the surface this appears to be related to the partial Center (P (Center) requirement discussion (see SWE-140), the key differences are (1) the implementation of P (Center) provides only partial relief from the full requirement, (2)  results of the SWE-120 waivers are intended to last for an extended time, and (3) they cover multiple instances of requirement relief. The SWE-140 application, on the other hand, is intended for a particular project's implementation and/or life cycle or a portion of its life cycle.

To assure the broad applicability of the request to a Center under SWE-120, the requestor makes certain that all work areas and/or elements of a Center's mission are reviewed, e.g., space, aeronautics, research, advanced technology, institutional infrastructure).

Note that NPR 1400.1E, NASA Directives and Charters Procedural Requirements 256 , only allows approval of request for waiver relief from NPRs for a specific period or duration.

(Editor note: Please contact the Handbook Development Team if you have an example of a general exclusion waiver request that is shareable with the software community.

4. Small Projects

Centers may wish to seek generic waivers to address limited resources on small projects for which Mission Directorates have documented their acceptance as being of high risk (see NPR 8705.4 048).

When small projects need to reduce the set of applicable software requirements due to constraints, the designated Center Software Technical Authority is to be consulted. Waivers and Deviations against NASA requirements are broadly covered in NPR 7120.5 082, section3.3, and specifically covered for software in Chapter 6 of NPR 7150.2 (with associated guidance in this Handbook). NASA Chief Engineer’s specific direction on waivers and Technical Authority is located on the

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. 262 NODIS maintains a web page 406   for the posting of approved waivers for general reference.

5. Resources

5.1 Tools

Tools relative to this SWE may be found in the table below. You may wish to reference the Tools Table in this handbook for an evolving list of these and other tools in use at NASA. Note that this table should not be considered all-inclusive, nor is it an endorsement of any particular tool. Check with your Center to see what tools are available to facilitate compliance with this requirement.

No tools have been currently identified for this SWE. If you wish to suggest a tool, please leave a comment below.

6. Lessons Learned

No Lessons Learned have currently been identified for this requirement.

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