bannera

Book A.
Introduction

Book B.
7150 Requirements Guidance

Book C.
Topics

Tools,
References, & Terms

SPAN
(NASA Only)


SWE-067 - Verify Implementation

1. Requirements

3.4.3 The project shall ensure that the implementation of each software requirement is verified to the requirement.

1.1 Implementation Notes from Appendix D

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

1.2 Applicability Across Classes

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.

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?

   

   

   

   

   

   

   

   

   

   

   

    P(C)

   

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

Requirements are the basis for a project. They identify the need to be addressed, the behavior of the system, and the constraints under which the problem is to be solved. They also specify the product to be delivered by a contracted provider of software.

To ensure that the resulting product was "built right" (addresses the need, provides the specified behavior, and performs within the stated constraints), the implementation (code) of those requirements needs to be verified against the requirements.

3. Guidance

Verification activities are not to be confused with validation activities as each has a specific goal. Verification is designed to confirm the product is being produced correctly while validation is designed to confirm the right system is being produced. Specific to a software project's implementation, verification involves confirming that the implementation (code) correctly, completely, consistently, and accurately includes each software requirement. Verification methods can include testing, analysis, demonstration, and inspection.

The NASA Independent Verification and Validation Technical Framework (IVV 09-1) document 003 states that "It is important to recognize that requirements cannot be evaluated in isolation. Requirements must be evaluated as a set in order to determine that a particular goal or behavior is being met."

Confirmation of software requirements implementation needs to occur at various times in the project life cycle to ensure that any issues are found and corrected as early as possible:

  • Completion of units of code.
  • Integration testing.
  • System testing.

Verification of requirements implementation includes the following objectives:

  • Ensure that the source code reliably performs capabilities stated in the requirements under nominal and off-nominal conditions, as applicable to the software classification (NASA IV&V Technical Framework 003, Revision M)
  • Ensure that the source code provides the reliability and fault tolerance stated in the requirements, as applicable to the software classification (NASA IV&V Technical Framework 003, Revision M)
  • Ensure that the source code satisfies functional, performance, and other requirements (Software Development Process Description Document 001, Revision R)

While the primary means of implementation verification is testing, the following analysis techniques are also useful (Software Development Process Description Document 001, Revision R). Note that these techniques are useful for detecting coding problems/issues and may not necessarily be required for verifying that the software properly implements the requirements unless the requirements include statements related to the complexity, memory usage, coding standards, etc.

  • McCabe complexity analysis (measures the number of linearly independent paths through a program's source code).
  • Memory analysis.
  • Static analysis.
  • Code standards checking.

Requirements implementation verification activities need to be planned and documented (SWE-104) and verification techniques can be included in the bidirectional requirements traceability matrix (SWE-072) to ensure that all requirements are verified in the implementation. Results of this activity are to be documented (SWE-069), evaluated (SWE-068), and defects corrected.

Consult Center Process Asset Libraries (PALs) for Center-specific guidance and resources related to implementation verification.

Additional guidance related to software testing, including specifics of plan, procedure, and report contents may be found in the following related requirements in this handbook:

SWE-028

Verification Planning

SWE-066

Perform Testing

SWE-068

Evaluate Test Results

SWE-069

Document Defects and Track

SWE-072

Bidirectional Traceability Between Software Test Procedures and Software

SWE-104

Software Test Plan

4. Small Projects

Small projects with few personnel could use a single document to describe the verification procedure as well as the test results rather than have the overhead of using separate documents.  

Small projects with few requirements may combine verification planning, the traceability matrix, and verification results into one product, rather than separate documents. This document may look like a verification matrix that identifies the requirements, type of verification for each requirement, any required tools, personnel, and/or environment needed for the verification, and the final results. The key for this requirement is to ensure the final product meets the content of the stated software requirements.

5. Resources

  • (SWEREF-001) Software Development Process Description Document, EI32-OI-001, Revision R, Flight and Ground Software Division, Marshall Space Flight Center (MSFC), 2010. See Chapters 16 and 17. This NASA-specific information and resource is available in Software Processes Across NASA (SPAN), accessible to NASA users from the SPAN tab in this Handbook.

  • (SWEREF-003)

    IVV 09-1, Revision P, NASA Independent Verification and Validation Program, Effective Date: February 26, 2016

  • (SWEREF-271)

    NASA STD 8719.13 (Rev C ) , Document Date: 2013-05-07

  • (SWEREF-478)

    Aerospace Report No. TOR-2004(3909)-3537, Revision B, March 11, 2005.


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

No Lessons Learned have currently been identified for this requirement.