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7150 Requirements Guidance

Book C.

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SWE-025 - Corrective Actions
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1. Requirements

2.2.14 The project shall ensure that corrective actions are taken, recorded, and managed to closure when actual results and performance deviate from the software plans.

1.1 Notes">1.1 Notes

NPR 7150.2 does not include any notes for this requirement.

1.2 Applicability Across Classes

Classes D and E and Safety Critical are labeled with "SO". This means that this requirement applies to the safety-critical aspects of the software.

Class G is labeled with "P (Center).  This means that an approved center-defined process which meets a non-empty subset of the full requirement can be used to achieve this requirement.





























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

The use of a good corrective action plan and related tools (usually referred to as a "PRACA" Problem Reporting and Corrective Action System) makes sure that the software development and assurance teams understand, act upon, and close issues and deviations to prevent reoccurrence.  Proper documentation helps the teams to track the activity, know when it is complete, and when it is eligible to be closed.  It also provides measurement data input for project metric evaluations and the development of lessons learned information.

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3. Guidance

The planning and requirements documentation developed during the early phases of the project (see SWE-013, SWE-102, and SWE-109) guides development of software work products. The project management team and the software development lead work together to construct a work plan that is logical and achievable in the allotted time. During early project phases key performance factors, schedules and milestones are composed. As scheduled work is performed it is important for the results to be reviewed to assure conformance with these plans and to assess if the expected performance has been achieved (see SWE-024).

Occasionally these reviews surface a significant deviation between the actual and expected results of an activity. Some deviations are a normal part of project development activity and are resolved through the normal course of scheduled activity. These deviations are typically tracked informally until the developers establish a product baseline, after which deviations/problems are formally tracked (usually in the PRACA system) which requires evaluation, disposition and assurance oversight of the problem.  The Software Development Plan or the Software Configuration Management Plan typically defines the level of the deviations that are required to be recorded and tracked in the formal tracking systems.   Typically a Center has an approved process for problem reporting and corrective action (PRACA) activities. This requirement does not mandate a particular approach or tool as long as the following key elements of a corrective action activity are employed.

During the course of the software development activity, once a deviation is found that meets the criteria for formal reporting, the software development team should clearly state the issue, its area of applicability across the software development activity, and the spectrum of relevant stakeholders it involves. As this information is obtained the issue is documented in the approved process tool or data repository and an analysis is conducted of the deviation. The results of the analysis should provide a clear understanding of the deviation and a proposed course of action to further investigate and resolve the deviation as necessary. SWE-113 provides specific details for the information needed for documenting a problem report.

The proposed course of action may be reviewed by project management and other relevant stakeholders to assure resources are available for the activity (see SWE-026). It may be necessary to update planning documentation and development schedules to account for the corrective action activity (see SWE-080).Once a corrective action activity has been approved and initiated, its progress is reviewed on a regular basis for progress and its use of planned resources.  This information is used to assess whether the action itself is on course or deviating from the expected result.

An important element of the corrective action activity is the proper closeout of the action. After the activity has concluded, or when the deviation has been narrowed to within acceptable limits, the closeout is recorded and may include the following information:

  • Description of the issue/deviation
  • Proposed corrective action, with acceptable limits
  • Actual results/impacts from the effort
  • Listing of required changes to requirements, schedules, resources, if any, to accommodate the result
  • Signature(s)/concurrence by all relevant stakeholders

Once the documentation has been completed, it should be entered into a suitable repository or configuration management system.

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4. Small Projects

This requirement applies to all projects.

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5. Resources

1.    NASA Systems Engineering Processes and Requirements with Change 1, NPR 7123.1A, 2009

2.    NASA Software Assurance Standard, NASA STD 8739.8, 2005

3.    NASA Space Flight Program and Project Management Requirements, NPR 7120.5D (NM-7120.81), 2009.

4.    NASA Software Formal Inspection Standard, NASA-STD-2202-93, 1993

5.1 Tools

Tools relative to this SWE may be found in the table above. If no tools are listed, none have been currently identified for this SWE. You may wish to reference table xyz 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.

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6. Lessons Learned

Probable Scenario for Mars Polar Lander Mission Loss (1998) Description: Neither the MPL software requirements specification nor the software, subsystem or system test plans required verification of immunity to transient signals. MPL touchdown sensors generated known transient signals at leg deployment. Full leg deployment test was not repeated after wiring corrections. Tests should be re-run after test deficiencies are corrected or hardware or software is revised unless clear rationale exists for not doing so. Hardware operational characteristics, including transients and spurious signals must be reflected in software requirements and verified by test..

Problem Reporting and Corrective Action System This Lesson Learned is based on Reliability Practice No. PD-ED-1255; from NASA Technical Memorandum 4322A, NASA Reliability Preferred Practices for Design and Test.

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