SAS_08_Legacy_Safety_Hill

Assurance and Recertification of Safety Critical Software In

Legacy Systems

Janie Hill

NASA Kennedy Space Center, FloridaJanice.L.Hill@nasa.gov

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Agenda

Problem/ApproachRelevance to NASAAccomplishmentsNext Steps

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Problem/Approach

The assurance of legacy systems from a safety perspective is of particular importance when reuse of the system is considered.

A problem arises when attempting to carry out the requirements of a software safety standard on real time legacy systems with safety-critical software.

We would like to be able to “recertify” these systems for use in other programs, such as Constellation.

To do this, we propose to make a “safety case” for these legacy systems.

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Problem/Approach

This proposed research is unique because it is designed to address the reverse engineering of the process and the risk of non-performance of safety requirements, for reuse and recertification of legacy software.

The NASA Safety Standard has a specific requirement to address the safety of legacy systems with safety-critical software, however no common methodology has been found to accomplish this requirement.

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Relevance to NASA Legacy systems with safety-critical software are abundant throughout NASA

and especially prevalent at KSC.

System Assurance Analyses (SAA) of the ground systems at KSC were performed many years ago. Some, if not all, of these analyses were performed without fully analyzing the software in the context of the system.

At the time the SAA’s were performed, the NASA Software Safety Standard was either not in existence, or was not required by the contract that produced the system.

Additionally, Safety Cases were not prepared for these ground systems.

Now, some of these systems may be candidate for reuse in the Constellation Program. We need to be able to “recertify” these systems as safe, including the software, per our NASA Safety requirements.

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AccomplishmentsJanuary 2008 – September 2008

Co-Authored and presented one paper on parts of the proposed methodology at the ASWEC 2008 in March 2008.

Completed the element and attribute definitions in the Software Safety Risk Taxonomy to complete the taxonomy.

Completed the questions for the Software Safety Taxonomy Based Questionnaire.

Interviewed the KCCS project manager using the TBQ

Developed risk statements based on the answers to the questions.

Analyzed the risks and bucketed the risks into risk areas.

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Accomplishments

• Initial Risk Data entry GUI is complete.

• This functionality now allows risks to be created and input into the database during the interviews with the projects.

• Traceability to the Taxonomy can now be created for each risk.

• Initial Safety Requirements GUI is complete.

• Safety requirements can be input into the database.

• Traceability to the Safety Taxonomy can now be created for each Safety Requirement.

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Next Steps Continue with implementation of the Legacy Systems Risk

Database.

Finish the Software Safety TBQ Graphical User Interface.

Finish the Software Requirements Specification for the LSRD.

Update the design documentation for the LSRD.

Work with Donna Smith at Wallops on their projects (October) and Chuck Niles at Langley.

Work with other projects at KSC (FY 09)

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Questions?