1. NASA-STD-8739.8B Title Material

DOCUMENT HISTORY LOG

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This NASA Technical Standard is published by the National Aeronautics and Space Administration (NASA) to provide uniform engineering and technical requirements for processes, procedures, practices, and methods that have been endorsed as standard for NASA facilities, programs, and projects, including requirements for selection, application, and design criteria of an item.
This standard was developed by the NASA Office of Safety and Mission Assurance (OSMA). Requests for information, corrections, or additions to this standard should be submitted to the OSMA by email to Agency-SMA-Policy-Feedback@mail.nasa.gov or via the “Email Feedback” link at https://standards.nasa.gov.

1. SCOPE

1.1 Document Purpose

1.1.1 The purpose of the Software Assurance and Software Safety Standard is to define the requirements to implement a systematic approach to software assurance, software safety, and Independent Verification and Validation (IV&V) for software created, acquired, provided, used, or maintained by or for NASA. Various personnel in the program, project, engineering, facility, or Safety and Mission Assurance (SMA) organizations can perform the activities required to satisfy these requirements. The Software Assurance and Software Safety Standard provides a basis for personnel to perform software assurance, software safety, and IV&V activities consistently throughout the life of the software.

1.1.2 The Software Assurance and Software Safety Standard, in accordance with NPR 7150.2, NASA Software Engineering Requirements, supports the implementation of the software assurance, software safety, and IV&V sub-disciplines. The application and approach to meeting the Software Assurance and Software Safety Standard vary based on the system and software products and processes to which they are applied. The Software Assurance and Software Safety Standard stresses coordination between the software assurance sub-disciplines and system safety, system reliability, hardware quality, system security, and software engineering to maintain the system perspective and minimize duplication of effort.

1.1.3 The objectives of the Software Assurance and Software Safety Standard include the following:

a. Ensuring that the processes, procedures, and products used to produce and sustain the software conform to all specified requirements and standards that govern those processes, procedures, and products.

(1) A set of activities that assess adherence to, and the adequacy of the software processes used to develop and modify software products.
(2) A set of activities that define and assess the adequacy of software processes to provide evidence that establishes confidence that the software processes are appropriate for and produce software products of suitable quality for their intended purposes.

b. Determining the degree of software quality obtained by the software products.
c. Ensuring that the software systems are safe and that the software safety-critical requirements are followed.
d. Ensuring that the software systems are secure.
e. Employing rigorous analysis and testing methodologies to identify objective evidence and conclusions to provide an independent assessment of critical products and processes throughout the life cycle.

1.1.4 The Software Assurance and Software Safety Standard is compatible with all software life cycle models. The Software Assurance and Software Safety Standard does not impose a particular life cycle model on a software project.

1.1.5 In this standard, all mandatory actions (i.e., requirements) are denoted by statements containing the term “shall.” The terms “may” denote a discretionary privilege or permission; “can” denotes statements of possibility or capability; “should” denotes a good practice and is recommended; but not required, “will” denotes expected outcome; and “are/is” denotes descriptive material.

1.2 Applicability

1.2.1 This standard is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers. This NASA Technical Standard applies to the assurance of software created by or for NASA projects, programs, facilities, and activities and defines the requirements for those activities. This directive is applicable to the Jet Propulsion Laboratory, a Federally Funded Research and Development Center, only to the extent specified in the NASA/Caltech Prime Contract. This standard may also apply to other contractors, grant recipients, or parties to agreements to the extent specified or referenced in their contracts, grants, or agreements.

1.3 Documentation and Deliverables

1.3.1 The Software Assurance and Software Safety Standard is not intended to designate the format of program/project/facility documentation and deliverables. The software assurance and software safety data, information, and plans may be considered to be quality records with a retention period as specified in NRRS 1441.1. The format of the documentation is a program/project/facility decision. The software assurance and software safety organizations should keep records, reports, metrics, analyses, and trending results and should keep copies of their project plans for future reference and improvements. The software assurance and software safety plans (e.g., the Software Assurance Plan) can be standalone documents or incorporated within other documents (e.g., part of a Software Management Plan, a Software Development Plan or part of a Program or Project Safety and Mission Assurance (SMA) plan).

1.4 Request for Relief

1.4.1 Tailoring of this standard for application to a specific program or project is documented as part of program or project requirements and approved by the responsible Center Technical Authority (TA) in accordance with NPR 8715.3, NASA General Safety Program Requirements. Section 4.5 of this standard contains the principles related to tailoring this standard’s requirements.

2. APPLICABLE AND REFERENCE DOCUMENTS

2.1 Applicable Documents

The applicable documents are accessible via the NASA Technical Standards System at https://standards.nasa.gov, or the NASA Online Directives Information System https://nodis3.gsfc.nasa.gov/main_lib.cfm or may be obtained directly from the Standards Developing Organizations.

• NPR 1400.1 NASA Directives and Charters Procedural Requirements
• NPR 7120.5 NASA Space Flight Program and Project Management Requirements
• NPR 7120.10 Technical Standards for NASA Programs and Projects
• PR 7150.2 NASA Software Engineering Requirements
• PR 8000.4 Agency Risk Management Procedural Requirements
• NPR 8715.3 NASA General Safety Program Requirements
• NASA-HDBK-2203 NASA Software Engineering Handbook
• NASA-HDBK-4008 Programmable Logic Devices Handbook
• NRRS 1441.1 NASA Records Retention Schedules

2.2 Reference Documents

The reference documents listed in this section are not incorporated by reference within this standard but may provide further clarification and guidance.

2.2.1 Government Documents

• NPD 2810.1 NASA Information Security Policy
• NPD 8720.1 NASA Reliability and Maintainability Program Policy
• NPR 1441.1 NASA Records Management Program Requirements
• NPR 2210.1 Release of NASA Software
• NPR 2810.1 Security of Information and Information Systems
• NPR 2830.1 NASA Enterprise Architecture Procedures
• NPR 2841.1 Identity, Credential, and Access Management
• NPR 7120.7 NASA Information Technology Program and Project Management Requirements
• NPR 7120.8 NASA Research and Technology Program and Project Management Requirements
• NPR 7120.10 Technical Standards for NASA Programs and Projects
• NPR 7120.11 Health and Medical Technical Authority Implementation
• NPR 7123.1 NASA Systems Engineering Processes and Requirements.
• NPR 8000.4 Agency Risk Management Procedural Requirements
• NPR 7123.1 NASA Systems Engineering Processes and Requirements
• NASA-STD-1006 Space System Protection Standard
• NASA-STD-2601 Minimum Cybersecurity Requirements for Computing Systems
• NASA-STD-7009 Standard for Models and Simulations
• NASA-STD-8729.1 NASA Reliability And Maintainability Standard For Spaceflight And Support Systems
• NASA-HDBK-7009 NASA Handbook for Models and Simulations: An Implementation Guide for NASA-STD-7009
• NASA-HDBK-8709.22 Safety and Mission Assurance Acronyms, Abbreviations, and Definitions
• NASA-HDBK-8739.23 NASA Complex Electronics Handbook for Assurance Professionals
• NIST SP 800-37 Risk Management Framework
• NIST SP 800-40 Guide to Enterprise Patch Management Planning: Preventive Maintenance for Technology
• NIST SP 800-53 Security and Privacy Controls for Information Systems and Organizations
• NIST SP 800-70 National Checklist Program for Information Technology products: Guidelines for Checklist Users and Developers
• NIST SP 800-115 Technical Guide to Information Security Testing and Assessment
• NFS 1813.301-79 Supporting Federal Policies, Regulations, and NASA Procedural Requirements
• NFS 1852.237-72 Access to Sensitive Information
• NFS 1852.237-73 Release of Sensitive Information

2.2.2 Non-Government Documents

• CMMI-DEV, V2.0 CMMI® for Development, Version 2.0
• IEEE 730 Institute of Electrical and Electronics Engineers (IEEE) Standard for Software Quality Assurance Processes
• IEEE 828 IEEE Standard for Configuration Management in Systems and Software Engineering.
• IEEE 982.1 IEEE Standard Measures of the Software Aspects of Dependability
• IEEE 1012 IEEE Standard for System, Software, and Hardware Verification and Validation
• IEEE 1028 IEEE Standard for Software Reviews and Audits
• IEEE 1633 IEEE Recommended Practice on Software Reliability
• IEEE 15026-1 Systems and software engineering--Systems and software assurance--Part 1: Concepts and vocabulary
• IEEE 29119-4 Software and systems engineering -- Software testing -- Part 4: Test techniques
• ISO 26514 Systems and software engineering–requirements for designers and developers of user documentation
• ISO 24765 System and Software Engineering – Vocabulary

2.3 Order of Precedence

2.3.1 This standard establishes requirements to implement a systematic approach to Software Assurance, Software Safety, and IV&V for software created, acquired, provided, or maintained by or for NASA but does not supersede nor waive established Agency requirements found in other documentation.

2.3.2 Conflicts between the Software Assurance and Software Safety Standard and other requirements documents are resolved by the responsible SMA and engineering TA(s), per NPR1400.1, NASA Directives and Charters Procedural Requirements, and NPR 7120.10, Technical Standards for NASA Programs and Projects.

3. ACRONYMS AND DEFINITIONS
3.1 Acronyms and Abbreviations
CMMI®? Capability Maturity Model Integration
COTS Commercial-Off-The-Shelf
GOTS Government-Off-The-Shelf
HDBK Handbook
IEEE Institute of Electrical and Electronics Engineers
IPEP IV&V Project Execution Plan
IV&V Independent Verification and Validation
MC/DC Modified Condition/Decision Coverage
MOTS Modified-Off-The-Shelf
NASA National Aeronautics and Space Administration
NIST National Institute of Standards and Technology
NPD NASA Policy Directive
NPR NASA Procedural Requirements
NRRS NASA Records Retention Schedule
OSMA NASA Headquarters Office, Safety and Mission Assurance
OSS Open Source Software
PLC Programmable Logic Controller
PROM Programmable Read-Only Memory
RTOS Real-Time Operating System
SMA Safety and Mission Assurance
SP Special Publication
SWE Software Engineering
TA Technical Authority
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3.2 Definitions
Accredit. The official acceptance of a software development tool, model, or simulation, including associated data, to use for a specific purpose.
Acquirer. The entity or individual who specifies the requirements and accepts the resulting software products. The Acquirer is usually NASA or an organization within the Agency but can also refer to the prime contractor-subcontractor relationship.
Analyze. Review results in-depth, look at relationships of activities, examine methodologies in detail, and follow methodologies such as Failure Mode and Effects Analysis, Fault Tree Analysis, trending, and metrics analysis. Examine processes, plans, products, and task lists for completeness, consistency, accuracy, reasonableness, and compliance with requirements. The analysis may include identifying missing, incomplete, or inaccurate products, relationships, deliverables, activities, required actions, etc.
Approve. When the responsible originating official, or designated decision authority, of a document, report, condition, etc., has agreed, via their signature, to the content and indicates the document is ready for release, baselining, distribution, etc. Usually, one “approver” and several stakeholders need to “concur” for official acceptance of a document, report, etc. For example, the project manager would approve the Software Development Plan, but SMA would concur on it.
Assess. Judge results against plans or work product requirements. Assess includes judging for practicality, timeliness, correctness, completeness, compliance, evaluation of rationale, etc., reviewing activities performed, and independently tracking corrective actions to closure.
Assure. When software assurance personnel make certain that others have performed the specified software assurance, management, and engineering activities.
Audit. Formal review to assess compliance with hardware or software requirements, specifications, baselines, safety standards, procedures, instructions, codes, and contractual and licensing requirements. (Source NPR 8715.3)
Bi-directional Traceability. Association among two or more logical entities that are discernible in either direction (to and from an entity). (Source IEEE Definition)
Concur. A documented agreement that a proposed course of action is acceptable.
Condition. (1) measurable qualitative or quantitative attribute that is stipulated for a requirement and that indicates a circumstance or event under which a requirement applies (2) description of a contingency to be considered in the representation of a problem, or a reference to other procedures to be considered as part of the condition (3) true or false logical predicate (4) logical predicate involving one or more behavior model elements (5) Boolean expression containing no Boolean operators.
Configuration Item. (1)item or aggregation of hardware, software, or both that is designated for configuration management and treated as a single entity in the configuration management process (2)component of an infrastructure or an item which is or will be under control of
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configuration management (3) aggregation of work products that is designated for configuration management and treated as a single entity in the configuration management process (4) any system element or aggregation of system elements that satisfies an end use function and is designated by the acquirer for separate configuration control (5) item or aggregation of software that is designed to be managed as a single entity and its underlying components, such as documentation, data structures, scripts. (Source IEEE Definition)
Note: Configuration items can vary widely in complexity, size, and type, ranging from an entire system including all hardware, software, and documentation, to a single module or a minor hardware component. CIs have four common characteristics: defined functionality; replaceable as an entity; unique specification; formal control of form, fit, and function. See Also: hardware configuration item, computer software configuration item, configuration identification, and critical item.
Confirm. Check to see that activities specified in the software engineering requirements are adequately done and evidence of the activities exists as proof. Confirm includes ensuring activities are done completely and correctly and have expected content according to approved tailoring.
Critical. A condition that may cause severe injury or occupational illness, or major property damage to facilities, systems, or flight hardware.
Deliverable. Product or item that has to be completed and delivered under the terms of an agreement or contract. Products may also be deliverables, e.g., software requirements specifications, and detailed design documents. Develop. To produce or create a product or document and mature or advance the product or document content.
Ensure. When software assurance or software safety personnel perform the specified software assurance and software safety activities themselves.
Event. (1) occurrence of a particular set of circumstances (2) external or internal stimulus used for synchronization purposes (3) change detectable by the subject software (4) fact that an action has taken place (5) singular moment in time at which some perceptible phenomenological change (energy, matter, or information) occurs at the port of a unit.
Failure. Inability of a system, subsystem, component, or part to perform its required function within specified limits. (Source NPR 8715.3)
Hazard. A state or a set of conditions, internal or external to a system that has the potential to cause harm. (Source NPR 8715.3)
Hazard Analysis. Identifying and evaluating existing and potential hazards and the recommended mitigation for the hazard sources found.
Hazard Control. Means of reducing the risk of exposure to a hazard. (Source NPR 8715.3)
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Hazardous Operation/Work Activity. Any operation or other work activity that, without the implementation of proper mitigations, has a high potential to result in loss of life, serious injury to personnel or public, or damage to property due to the material or equipment involved or the nature of the operation/activity itself.
Independent Verification and Validation. Verification and validation performed by an organization that is technically, managerially, and financially independent of the development organization. (Source IEEE Definition)
Inhibit. Design feature that prevents the operation of a function.
Insight. An element of Government surveillance that monitors contractor compliance using Government-identified metrics and contracted milestones. Insight is a continuum that can range from low intensity such as reviewing quarterly reports to high intensity such as performing surveys and reviews. (Source NPR 7123.1)
Maintain. To continue to have; to keep in existence, to stay up-to-date and correct.
Mission Critical. [1] Item or function that must retain its operational capability to assure no mission failure (i.e., for mission success). [2] An item or function, the failure of which may result in the inability to retain operational capability for mission continuation if corrective action is not successfully performed. (Source NASA-STD-8729.1)
Mission Success. Meeting all mission objectives and requirements for performance and safety. (Source NPR 8715.3)
Monitor. (1) software tool or hardware device that operates concurrently with a system or component and supervises, records, analyzes, or verifies the operation of the system or component; (2) collect project performance data with respect to a plan, process, produce performance measures, and report and disseminate performance information.
Participate. To be a part of the activity, audit, review, meeting, or assessment.
Perform. Software assurance does the action specified. Perform may include making comparisons of independent results with similar activities performed by engineering; performing audits; and reporting results to engineering.
Product. A result of a physical, analytical, or another process. The item delivered to the customer (e.g., hardware, software, test reports, data) and the processes (e.g., system engineering, design, test, logistics) that make the product possible. (Source NASA-HDBK-8709.22)
Program. A strategic investment by a Mission Directorate or Mission Support Office that has a defined architecture and technical approach, requirements, funding level, and management structure that initiates and directs one or more projects. A program implements a strategic direction that the Agency has identified as needed to accomplish Agency goals and objectives. (Source NPR 7120.5)
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Program Manager. A generic term for the person who is formally assigned to be in charge of the program. A program manager could be designated as a program lead, program director, or some other term, as defined in the program's governing document. A program manager is responsible for the formulation and implementation of the program, per the governing document with the sponsoring MDAA.
Project. A specific investment having defined goals, objectives, requirements, life cycle cost, a beginning, and an end. A project yields new or revised products or services that directly address NASA’s strategic needs. They may be performed wholly in-house; by Government, industry, academia partnerships; or through contracts with private industry. (Source NPR 7150.2)
Project Manager. The entity or individual who accepts the resulting software products. Project managers are responsible and accountable for the safe conduct and successful outcome of their program or project in conformance with governing programmatic requirements. The project manager is usually NASA but can also refer to the prime contractor-subcontractor relationship as well.
Provider. A Provider is a NASA or contractor organization that is tasked by an accountable organization (i.e., the Acquirer) to produce a product or service. (Source NASA-HDBK-8709.22)
Regression testing. (1) selective retesting of a system or component to verify that modifications have not caused unintended effects and that the system or component still complies with its specified requirements (2) testing following modifications to a test item or its operational environment, to identify whether regression failures occur. (Source IEEE Definition)
Risk. The combination of (1) the probability (qualitative or quantitative) of experiencing an undesired event, (2) the consequences, impact, or severity that would occur if the undesired event were to occur, and (3) the uncertainties associated with the probability and consequences. (Source NPR 8715.3)
Note: A risk is an uncertain future event, or combination of events, that could threaten the achievement of performance objectives or requirements. A "problem," on the other hand, describes an issue that is certain or near certain to exist now, or an event that has been determined with certainty or near certainty to have occurred and is threatening the achievement of an objective or requirement. It is generally at the discretion of the decision authority to define at what level of certainty (i.e., likelihood) an event may be classified and addressed as a “problem” rather than as a “risk.” A risk may be conditional upon a problem, i.e., an existing issue may or may not develop into performance-objective consequences or the extent to which it may be at present uncertain.
Risk Posture. A characterization of risk based on conditions (e.g., criticality, complexity, environments, performance, cost, schedule) and a set of identified risks, taken as a whole which allows an understanding of the overall risk or provides a target risk range or level, which can then be used to support decisions being made.
Safe State. A system state in which hazards are inhibited, and all hazardous actuators are in a non-hazardous state. The system can have more than one Safe State.
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Safety. Freedom from those conditions that can cause death, injury, occupational illness, damage to or loss of equipment or property, or damage to the environment. In a risk-informed context, safety is an overall mission and program condition that provides sufficient assurance that accidents will not result from the mission execution or program implementation, or, if they occur, their consequences will be mitigated. This assurance is established by means of the satisfaction of a combination of deterministic criteria and risk criteria. (Source NPR 8715.3)
Safety Analysis. Generic term for a family of analyses, which includes but is not limited to, preliminary hazard analysis, system (subsystem) hazard analysis, operating hazard analysis, software hazard analysis, sneak circuit, and others. Software safety analysis consists of a number of tools and techniques to identify safety risks and formulate effective controls. These techniques are used to help identify the hazards during the Hazard Analysis process, which in turn identifies the safety-critical software. The Safety Analysis techniques often used to support the Hazard Analysis are the Software Fault Tree Analysis and the Software Failure Modes and Effects Analysis. The Software Fault Tree Analysis and the Software Failure Modes and Effects Analysis are used to help identify hazards, hazard causes, and potential failure modes.
Safety-Critical. A term describing any condition, event, operation, process, equipment, or system that could cause or lead to severe injury, major damage, or mission failure if performed or built improperly or allowed to remain uncorrected. (Source NPR 8715.3)
Safety-Critical Software. Software is classified as safety-critical if the software is determined by and traceable to a hazard analysis. Software is classified as safety-critical if it meets at least one of the following criteria:
a. Causes or contributes to a system hazardous condition/event,
b. Controls functions identified in a system hazard,
c. Provides mitigation for a system hazardous condition/event,
d. Mitigates damage if a hazardous condition/event occurs,
e. Detects, reports, and takes corrective action if the system reaches a potentially hazardous state.
Software. defined as (1) computer programs, procedures, and associated documentation and data pertaining to the operation of a computer system (2) all or a part of the programs, procedures, rules, and associated documentation of an information processing (3) program or set of programs used to run a computer (4) all or part of the programs which process or support the processing of digital information (5) part of a product that is the computer program or the set of computer programs. This definition applies to software developed by NASA, software developed for NASA, software maintained by or for NASA, Commercial-Off-The-Shelf (COTS), Government-Off-The-Shelf (GOTS), Modified-Off-The-Shelf (MOTS), Open Source Software (OSS), reused software components, auto-generated code, embedded software, the software executed on processors embedded in programmable logic devices (see NASA-HDBK-4008), legacy, heritage, applications, freeware, shareware, trial or demonstration software, and OSS components. (Source NPR 7150.2)
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Software Assurance. (1) a set of activities that assess adherence to, and the adequacy of the software processes used to develop and modify software products. Software assurance also determines the degree to which the desired results from software quality control are being obtained. (2) set of activities that define and assess the adequacy of software processes to provide evidence that establishes confidence that the software processes are appropriate for and produce software products of suitable quality for their intended purposes. (Source IEEE Definition)
Note: A key attribute of software assurance is the objectivity of the software assurance function with respect to the project.
Software Developer. A person, organization, or system that develops software based on program/project requirements.
Software Life Cycle. The period that begins when a software product is conceived and ends when the software is no longer available for use. The software life cycle typically includes a concept phase, requirements phase, design phase, implementation phase, test phase, installation and checkout phase, operation and maintenance phase, and sometimes, retirement phase.
Software Peer Review. An examination of a software product to detect and identify software anomalies, including errors and deviations from standards and specifications. (Source IEEE Definition)
Software Safety. The aspects of software engineering, system safety, and software assurance, that provide a systematic approach to identifying, analyzing, tracking, mitigating, and controlling hazards and hazardous functions of a system where software may contribute either to the hazard(s) or to its detection, mitigation or control, to ensure safe operation of the system.
Software Validation. (1)confirmation, through the provision of objective evidence, that the requirements for a specific intended use or application have been fulfilled (2) process of providing evidence that the system, software, or hardware and its associated products satisfy requirements allocated to it at the end of each life cycle activity, solve the right problem (e.g., correctly model physical laws, implement business rules, and use the proper system assumptions), and satisfy intended use and user needs (3) the assurance that a product, service, or system meets the needs of the customer and other identified stakeholders (4) process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements (5) confirmation in a timely manner, through automated techniques where possible, through the provision of objective evidence, that the requirements for a specific intended use or application have been fulfilled. (Source IEEE Definition)
Note: Validation in a system life cycle context is the set of activities ensuring and gaining confidence that a system is able to accomplish its intended use, goals, and objectives (meet stakeholder requirements) in the intended operational environment. The right system has been built or is operating to meet business objectives. Validation demonstrates that the system can be used by the users for their specific tasks. "Validated" is used to designate the corresponding status. Multiple Validation can be carried out if there are different intended uses.
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Software Verification. Confirmation that products properly reflect the requirements specified for them. In other words, verification ensures that “you built it right.” (Source IEEE Definition)
Supplier. Any organization which provides a product or service to a customer. By this definition, suppliers may include vendors, subcontractors, contractors, flight programs/projects, and the NASA organization supplying science data to a principal investigator. The classical definition of a supplier is a subcontractor, at any tier, performing contract services or producing the contract articles for a contractor. (Source NASA-HDBK-8709.22)
System Safety. Application of engineering and management principles, criteria, and techniques to optimize safety and reduce risks within the constraints of operational effectiveness, time, and cost.
Tailoring. The process used to adjust a prescribed requirement to accommodate the needs of a specific task or activity (e.g., program or project). Tailoring may result in changes, subtractions, or additions to a typical implementation of the requirement. (Source NPR 7150.2) Track. To follow and note the course or progress of the product.

4. SOFTWARE ASSURANCE AND SOFTWARE SAFETY REQUIREMENTS

4.1 Software Assurance Description

4.1.1 The Software Assurance activities provide a level of confidence that software is free from vulnerabilities, either intentionally designed into the software or accidentally inserted at any time during its life cycle, that the software functions in an intended manner, and that the software does not function in an unintended manner. The objectives of the Software Assurance and Software Safety Standard include the following:

a. Ensuring that the processes, procedures, and products used to produce and sustain the software conform to all specified requirements and standards that govern those processes, procedures, and products.

(a) A set of activities that assess adherence to, and the adequacy of the software processes used to develop and modify software products.
(b) A set of activities that define and assess the adequacy of software processes to provide evidence that establishes confidence that the software processes are appropriate for and produce software products of suitable quality for their intended purposes.

b. Determining the degree of software quality obtained by the software products.
c. Ensuring that the software systems are safe and that the software safety-critical requirements are followed.
d. Ensuring that the software systems are secure.
e. Employing rigorous analysis and testing methodologies to identify objective evidence and conclusions to provide an independent assessment of critical products and processes throughout the life cycle.

4.1.2 Project and SMA Management support of the software assurance function is essential for software assurance, software safety, and IV&V processes to be effective. The software assurance, software safety, and IV&V support include the following:

a. The Project and SMA Management are familiar with and understand the software assurance, software safety, and IV&V function’s purposes, concepts, practices, and needs.
b. The Project and SMA Management provide the software assurance, software safety, and IV&V activities with skilled resources (people, equipment, knowledge, methods, facilities, and tools) to accomplish their project responsibilities.
c. The Project and SMA Management act upon information provided by the software assurance, software safety, and IV&V function throughout a project.

4.1.3  The Software Assurance and Software Safety Standard’s requirements apply to organizations in their roles as both Acquirers and Providers.

4.2 Safety-Critical Software Determination

Software is classified as safety-critical if the software is determined by and traceable to a hazard analysis. Software is classified as safety-critical if it meets at least one of the following criteria:

a. Causes or contributes to a system hazardous condition/event,

b. Controls functions identified in a system hazard,

c. Provides mitigation for a system hazardous condition/event,

d. Mitigates damage if a hazardous condition/event occurs,

e. Detects, reports, and takes corrective action if the system reaches a potentially hazardous state.

4.3 Software Assurance and Software Safety Requirements

4.3.1  The responsible project manager shall ensure the performance of the software assurance, software safety, and IV&V activities, the applicable requirements are defined in Table 1. In this document, the phrase “Software Assurance and Software Safety Tasks” means that the roles and responsibilities for completing these requirements may be delegated within the project consistent with the scope and scale of the project. The Center SMA Director designates SMA TA(s) for programs, facilities, and projects, providing direction, functional oversight, and assessment for all Agency software assurance, software safety, and IV&V activities. 

Table 1. Software Assurance and Software Safety Requirements Mapping Matrix

4.4 Independent Verification & Validation Requirements

4.4.1 IV&V Overview

4.4.1.1  IV&V is a technical discipline of software assurance that employs rigorous analysis and testing methodologies to identify objective evidence and conclusions to provide an independent assessment of critical products and processes throughout the software development life The evaluation of products and processes throughout the life cycle demonstrates whether the software is fit for nominal operations (required functionality, safety, dependability, etc.) and off-nominal conditions (response to faults, responses to hazardous conditions, etc.). The goal of the IV&V effort is to contribute assurance conclusions provided to the project and stakeholders based on evidence found in software development artifacts and risks associated with the intended behaviors of the software.

4.4.1.2  Three parameters define the independence of IV&V: technical independence, managerial independence, and financial independence.

1. Technical independence requires that the personnel performing the IV&V analysis are not involved in the development of the system or its elements. The IV&V team establishes an understanding of the problem and how the system addresses the problem. Through technical independence, the IV&V team’s different perspective allows it to detect subtle errors overlooked by personnel focused on developing the system.
2. Managerial independence requires that the personnel performing the IV&V analysis are not in the same organization as the development and program management team. Managerial independence also means that the IV&V team makes its own decisions about which segments of the system and its software to analyze and test, chooses the IV&V analysis methods to apply, and defines the IV&V schedule of activities. While independent from the development and program management organization, the IV&V team provides its findings in a timely manner to both of those organizations. The submission of findings to the program management organization should not include any restrictions (e.g., requiring the approval of the development organization) or any other adverse pressures from the development group.
3. Financial independence requires that the control of the IV&V budget be vested in a group independent of the software development organization. Financial independence does not necessarily mean that the IV&V team controls the budget but that the finances should be structured so that funding is available for the IV&V team to complete its analysis or test work. No adverse financial pressure or influence is applied.

4.4.1.3  The IV&V process starts early in the software development life cycle, providing feedback to the IV&V provider organization, allowing the IV&V team to modify products at optimal timeframes and in a timely fashion, thereby reducing overall project risk. The feedback also answers project stakeholders’ questions about system properties (correctness, robustness, safety, security, etc.) to make informed decisions with respect to the development and acceptance of the system and its software.

4.4.1.4  The IV&V provider performs two primary activities, often concurrently: verification and validation. Each of the activities provides a different perspective on the system/software.

1. Verification is the process of evaluating a system and its software to provide objective evidence as to whether or not a product conforms to the build-to requirements and design specifications. Verification holds from the requirements through the design and code and into testing. Verification demonstrates that the products of a given development phase satisfy the conditions imposed at the start of or during that phase.
2. Validation develops objective evidence that shows that the content of the engineering artifact is the right content for the developed system/software.

The content is accurate and correct if the objective evidence demonstrates that it satisfies the system requirements (e.g., user needs, stakeholder needs, etc.), fully describes the required capability/functionality needed, and solves the right problem.

4.4.1.5  The main goal of the IV&V effort is to identify and generate objective evidence that supports the correct operation of the system or refutes the correct operation of the system. The IV&V provider typically works with the development team to understand this objective evidence, which provides artifacts such as concept studies, operations concepts, and requirements that define the overall project. The IV&V provider uses these materials to develop an independent understanding of the project’s commitment to NASA, which forms the basis for validating lower-level technical artifacts.

4.4.1.6  Two principles help guide the development and use of objective evidence.

1. Performing IV&V throughout the entire development lifetime is the first principle; potential problems should be detected as early as possible in the development life Performing IV&V throughout the entire development lifetime provides the IV&V team with sufficient information to establish a basis for the analysis results and provides early objective evidence to the development and program management groups to help keep the development effort on track early in the life cycle.
2. The second principle is “appropriate assurance.” Given that it is not possible to provide IV&V on all aspects of a project’s software, the IV&V provider and project should balance risks against available resources to define an IV&V program for each project that provides IV&V so that the software will operate correctly, safely, reliably, and securely throughout its operational lifetime. The IPEP documents this tailored approach and summarizes the cost/benefit trade-offs made in the scoping process.

4.4.1.7  The IV&V requirements are analyzed and partitioned according to the type of artifact. The requirements do not imply or require the use of any specific life cycle model. It is also important to understand that IV&V applies to any life cycle development process. The IV&V requirements document the potential scope of analysis performed by the IV&V provider and the key responsibility of the software project to provide the information needed to perform that analysis. Additionally, the risk assessment is used to scope the IV&V analysis to help determine the prioritization of activities and the level of rigor associated with performing those activities. The scoping exercise results are captured in the IV&V Project Execution Plan, as documented below.

4.4.2 IV&V Requirements

The responsible project manager shall ensure the performance of the IV&V requirements, as defined in section 4.4.2 of this standard. The IV&V requirements in this section of the standard apply to any project required to have IV&V per the criteria defined in the NASA Software Engineering Requirements, NPR 7150.2. The IV&V requirements apply to all IV&V efforts performed on a software development project, as tailored by the IV&V Project Execution Plan. The IV&V requirements also serve as the definition of what NASA considers IV&V. IV&V is a risk mitigation activity, and as such, the application of IV&V analysis and the rigor of that analysis is driven by the IV&V provider’s assessment of software risk.

4.4.2.1 The IV&V provider shall conduct planning and risk assessments to determine the specific system/software behaviors (including the software components responsible for implementing the behaviors) to be analyzed.

4.4.2.2 The IV&V provider shall develop and negotiate an IV&V IPEP with the project.

4.4.2.3 The Project SMA Technical Authority (TA) shall review and concur with the IPEP.

4.4.2.4 The IV&V provider shall provide analysis results, risks, and assurance statements and data to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.5 The IV&V provider shall participate in project reviews of software activities. Participation includes providing status and results of software IV&V activities including, but not limited to, upcoming analysis activities, artifacts needed from the project, the results of the current or completed analysis, defects, and risks to stakeholders, customers, and development project personnel.

4.4.2.6 The IV&V provider shall provide the responsible organizations’ project management, engineering, and software assurance personnel insight into the software IV&V and IV&V test activities. As a minimum, the IV&V provider will be required to allow the responsible organizations’ project management, engineering, and software assurance personnel to perform the following activities:

1. Monitor the IV&V activities and plans.
2. Review the verification activities to ensure adequacy.
3. Review IV&V studies and source data.
4. Audit the software IV&V processes and practices.
5. Participate in IV&V software reviews and technical interchange meetings

4.4.2.7 The IV&V provider shall participate in planned software peer reviews or software inspections guided by the planning and scoping risk analysis documented in the IPEP and NASA-HDBK-2203.

4.4.2.8 The IV&V provider shall establish, record, maintain, report, and utilize IV&V management and technical measurements.

4.4.2.9 The IV&V provider shall assess and track software activities' actual results and performance against the software plans and identify and report any risks or findings to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.10 The IV&V provider shall track and evaluate changes to software products to evaluate for possible changes in the IV&V provider’s risk analysis and potential adverse impacts to the software system and the development effort.

4.4.2.11 The IV&V provider shall assess the software development life cycle for suitability for the problem to be solved and identify and communicate any risks associated with the chosen life cycle to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.12 The IV&V provider shall identify, analyze, track, and record risks to the software and development project in accordance with NPR 8000.4, Agency Risk Management Procedural Requirements, and communicate the risks to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.13 The IV&V provider shall verify the project implements the requirements for software listed in NPR 7150.2 and communicate any risks to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.14 The IV&V provider shall track, record, and communicate defects/issues and other results found during the execution of IV&V analysis and independent IV&V testing to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.15 The IV&V provider shall ensure that the identified defects and issues are addressed by the project.

4.4.2.16 The IV&V provider shall ensure that software planned for reuse meets the fit, form, and function as a component within the new application.

4.4.2.17 The IV&V provider shall ensure that the system architecture contains the computing-related items (subsystems, components, etc.) to carry out the system's mission and satisfy user needs and operational scenarios or use cases.

4.4.2.18 The IV&V provider shall ensure that the basis for the computing-related functions reflects the planned operations and mission objectives.

4.4.2.19 The IV&V provider shall ensure that feasibility and trade studies provide the results to support the critical decisions that drove the need for the study.

4.4.2.20 The IV&V provider shall ensure that known software-based hazard causes, contributors, and controls are identified, documented, and traced to the project requirements.

4.4.2.21 The IV&V provider shall ensure that known security threats and risks are identified, appropriately documented, and updated throughout the software development life cycle and communicated to the responsible organizations’ project management, engineering, and software assurance personnel.

4.4.2.22 The IV&V provider shall verify and validate that the software requirements and system requirements are, as a minimum, correct, consistent, complete, accurate, readable, traceable, and testable.

4.4.2.23 The IV&V provider shall verify and validate that the mitigations for identified security risks are in the software requirements.

4.4.2.24 The IV&V provider shall ensure that software requirements meet the dependability and fault tolerance required by the system.

4.4.2.25 The IV&V provider shall ensure that software requirements provide the capability of controlling identified hazards and do not create hazardous conditions.

4.4.2.26 The IV&V provider shall verify and validate that the relationship between the in-scope system/software requirements and the associated architectural elements is traceable, correct, consistent, and complete.

4.4.2.27 The IV&V provider shall verify and validate that the software architecture meets the user’s safety and mission-critical needs as defined in the requirements.

4.4.2.28 The IV&V provider shall verify and validate that the detailed design products are traceable, consistent, complete, accurate, and testable.

4.4.2.29 The IV&V provider shall verify and validate that the interfaces between the detailed design components and the hardware, users, operators, other software, and external systems are correct, consistent, complete, accurate, and testable.

4.4.2.30 The IV&V provider shall verify and validate that the relationship between the software requirements and the associated detailed design components is correct, consistent, and complete.

4.4.2.31 The IV&V provider shall verify and validate that the software code and data products are consistent with architecture, complete with respect to requirements, and testable.

4.4.2.32 The IV&V provider shall verify and validate that the software code meets the industry best practices and software coding standards.

4.4.2.33 The IV&V provider shall verify and validate that the security risks in the software code are identified and mitigated.

4.4.2.34 The IV&V provider shall verify and validate the appropriate use of off-the-shelf software, including ensuring that the project has identified all OSS used and that the security risks are identified and mitigated by the use of the off-the-shelf

4.4.2.35 The IV&V provider shall verify and validate that the project assesses the software systems for possible security vulnerabilities and weaknesses.

4.4.2.36 The IV&V provider shall verify and validate that the project implements the required software security risk mitigations to ensure that security objectives for software are satisfied.

4.4.2.37 The IV&V provider shall verify and validate the source code through the use of analysis tools (including but not limited to static, dynamic, composition, and formal analysis tools).

4.4.2.38 The IV&V provider shall verify and validate that the relationship between the software design elements and the associated software units is correct, consistent, and complete.

4.4.2.39 The IV&V provider shall verify and validate that the relationship between software code components and corresponding requirements is correct, complete, and consistent.

4.4.2.40 The IV&V provider shall verify and validate that test plans, test procedures, test cases, test environment (including simulations), and test design at all levels of testing (unit, integration, system, acceptance, etc.) are correct, complete, and consistent for verification and validation of the source code and system functions allocated to the software.

4.4.2.41 The IV&V provider shall verify and validate the relationships between the test plans, test procedures, test cases, test design, source code. and system functions allocated to the software are correct, complete, and consistent.

4.4.2.42 The IV&V provider shall verify that the test plans, test cases, test design, and test procedures contain objective acceptance criteria that support the verification of the associated requirements for both nominal and off-nominal conditions.

4.4.2.43 The IV&V provider shall verify that the software test results meet the associated acceptance criteria to ensure that the software correctly implements the associated requirements.

4.4.2.44 The IV&V provider shall verify that the project tests the required software security risk mitigations to ensure that the security objectives for the software are satisfied.

4.4.2.45 The IV&V provider shall verify that code coverage is measured by analysis of the results of the execution of tests.

4.4.2.46 The IV&V provider shall verify through independent testing each of the software requirements that trace to a hazardous event, cause, or mitigation technique.

4.4.2.47 The IV&V provider shall verify the project’s acceptance tests for loaded or uplinked data, rules, and code that affects software and software system behavior.

4.4.2.48 The IV&V provider shall participate in all NASA quality audits, assessments, and reviews associated with the project.

4.4.2.49 The IV&V provider shall assess the software maintenance and operational risks concerning software elements to support the planning of IV&V activities during the maintenance phase.

4.5 Principles Related to Tailoring the Standard Requirements

4.5.1  The SMA TA for the project shall review and approve any tailored Software Assurance and Software Safety Standard requirements.

4.5.2  Software requirements tailoring is the process used to seek relief from standard requirements consistent with program or project objectives, acceptable risk, and constraints. To accommodate the wide variety of software systems and subsystems, applying these requirements to specific software assurance, software safety, and IV&V efforts may be tailored where justified and approved. NASA established the TA governance model to approve and mitigate any changes to the Software Assurance and Software Safety Standard requirements. Tailoring from requirements in the Software Assurance and Software Safety Standard is governed by the
following steps. Tailoring at the Center level is decided by the SMA TA and the NPR 7150.2 Requirements Mapping Matrix applicability. Tailor the software assurance, software safety, and IV&V requirements using the following levels:

a. The first level of tailoring is the Software Classification Decision, see NPR 7150.2.

b. The second level of tailoring is the project’s Software Requirements Mapping Matrix, see NPR 7150.2.

c. The third level of tailoring is the tailoring by the Software Assurance TA of the Software Assurance and Software Safety Standard requirements that correspond to the project’s Software Requirements Mapping Matrix requirements.

4.5.3  The Software Assurance and Software Safety Standard establishes a baseline set of requirements for software assurance, software safety, and IV&V to reduce risks on NASA projects and programs. Each project has unique circumstances, and tailoring can modify the requirements set for software assurance, software safety, and IV&V effort. Determining the tailoring of requirements is a joint software engineering effort and SMA effort, including acceptable technical and programmatic risk posture, Agency priorities, size, and complexity. Requirements can be tailored more broadly across a group of similar projects, programs, organizations, or other collections of similar software development efforts.

4.5.4  Per SWE-121, the software assurance organization maintains a Requirements Mapping Matrix or multiple Requirements Mapping Matrices against requirements in the Software Assurance and Software Safety Standard, including those delegated to other parties or accomplished by contract vehicles. Per SWE-013 and SWE-039, the software assurance organization conducts risk assessment efforts to determine the software assurance, software safety, and IV&V tasks to be performed and the rigor of each task.

4.5.5  The request for relief from a requirement includes the rationale, a risk evaluation, and reference to all material that justifies supporting acceptance. The organization submitting the tailoring request informs the next higher level of involved management of the tailoring request in a timely manner. The dispositioning organization reviews the request with the other organizations that could be impacted or have a potential risk (i.e., to safety, quality, cybersecurity, health) with the proposed changes and obtains the concurrence of those organizations.

4.5.6  If a system or subsystem development evolves to meet a higher or lower software classification defined in NPR 7150.2, the software assurance, software safety, and IV&V organizations shall update their plan(s) to fulfill the applicable requirements per the Requirements Mapping Matrix and any approved changes and initiate adjustments to applicable contracts to meet the modified requirements.

4.5.7  The responsibilities for approving changes to the software engineering requirements are in NPR 7150.2. When the requirement and software class are applicable, the projects record the risk and rationale for any requirement not completely implemented by the project. The projects can document their related mitigations and risk acceptance in the approved Requirements Mapping Matrix.

Appendix A. GUIDELINES FOR THE HAZARD DEVELOPMENT INVOLVING SOFTWARE

A.1 Software Contributions to Hazards
A.1.1 Hazard Analysis should consider software’s ability, by design, to cause or control a given hazard. It is a best practice to include the software within the system hazard analysis. The general hazard analysis should consider software common-mode failures that can occur in instances of redundant flight computers running the same software.
A.1.2 Software safety analysis supplements the system hazard analysis by assessing the software performing critical functions serving as a hazard cause or control. A typical software safety analysis process identifies the must work and must not work functions in the hazard reports. The system hazard analysis and software safety analysis process should assess each function for compliance with the levied functional software requirements. The system hazard analysis and software safety analysis also assure the redundancy management performed by the software supports fault tolerance requirements.
A.1.3 The second part of the safety review should complete the design analysis portion of software safety analysis. The software safety analysis supports a requirements gap analysis to identify gaps (SWE-184) and ensure the risk and control strategy documented in hazard reports is correct, as stated. The system hazards analysis and software safety analysis support test plans' analysis to assure adequate off-nominal scenarios (SWE-62, SWE-65). Finally, the system hazards analysis should verify the final implementation and uphold the analysis by ensuring test results permit the closure of hazard verifications (SWE-68).
A.1.4 Considerations when identifying software causes in a general software-centric hazard analysis are found in Table 2 below.