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Book A.
Introduction

Book B.
7150 Requirements Guidance

Book C.
Topics

Tools,
References, & Terms

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SWE-120 - General Exclusion from Requirements
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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">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).

1.2 Applicability Across Classes

KEEP THIS SENTENCE IF THERE ARE NOT NOTES. REMOVE IF THERE ARE:
Appendix D of NPR 7150.2A does not include any notes for this requirement.

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

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2. Rationale

Centers and multi-Center projects typically create local directives and processes which 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 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 (e.g. Constellation program Computing System Requirements; Constellation Architecture Requirements Document). 

The issuance of generic  waiver coverage provides a Center's and major program/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.

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3. Guidance

The scope and duration of the requested generic waiver are especially important consideration s. NPRs and Center Directives are typically updated in five year cycles, making  this a reasonable upper limit for waiver duration in this situation.  The programs/projects lifecycle 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 are closely scrutinized by NASA Headquarters' Chief Engineer as unintended risks to current and future projects are difficult to analyze.  NASA has well documented classifications for project categories & priority levels, (NPRs 7120.5; 7120.7; and 7120.8), payload categories (NPR 8705.4), software classification and whether its Safety Critical (NPR 7150.2 & NASA-STD -8739.8). Its 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. Requesters are to ensure that risks are well documented with sound rational e in the waiver request. In some instances alternative techniques can mitigate these risks. The mitigating factors are documented so the Technical Authority 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 of NPR 7150.2's 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 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 projects' risk profile unnecessarily,  reduces safety, or impacts quality.

While this on the surface appears to be related to partial Center (P (Center) (see requirement discussion of SWE-140)  the key differences are; 1) 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) cover multiple instances of the of requirement  relief. The SWE-140 application, on the other hand, is intended for a particular project's implementation and/or lifecycle, or a portion of its lifecycle.

In order 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. only allows approval of request for waiver relief from NASA Procedural Requirements for a specific period or duration.

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4. Small Projects

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

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5. Resources

  1. NASA Directives Procedural Requirements, with Change 5 (11/19/2009), NPR 1400.1E, 2009. 
  2. NASA Space Flight Program and Project Management Requirements, NPR 7120.5D (NM-7120.81, 2009.
  3. NASA  Risk Classification for NASA Payloads , NPR 8705.4, 2008
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6. Lessons Learned

No Lessons Learned have currently been identified for this topic.

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