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System and Software Reliability Dolores R. Wallace SRS Technologies Software Assurance Technology Center http://satc.gsfc.nasa.gov / Dr. William H. Farr, Dr. John R. Crigler Naval Surface Warfare Center Dahlgren Division Dr. Swapna Gokhale. NASA OSMA SAS '04. Overview of the Problem.

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  1. System and Software ReliabilityDolores R. WallaceSRS TechnologiesSoftware Assurance Technology Centerhttp://satc.gsfc.nasa.gov/Dr. William H. Farr, Dr. John R. CriglerNaval Surface Warfare Center Dahlgren DivisionDr. Swapna Gokhale NASA OSMA SAS '04 SAS 04/ GSFC/SATC-NSWC-DD

  2. Overview of the Problem • Reliability Measurement is a critical objective for NASA systems • Systems are assessed from the software/hardware/systems perspective • Methodologies for hardware reliability assessment have been developed and utilized over the past several decades • Methodologies for software reliability assessment have been developed since the 70’s and have been utilized over the last twenty years • Methodologies for system reliability assessment have only been addressed over the last 10 years with little application experience • Tool is needed that integrates all aspects of reliability data (software, hardware, and systems perspectives) SAS 04/ GSFC/SATC-NSWC-DD

  3. Research Approach • To enhance the capability for NASA to assess system and software reliability by identifying and incorporating recent models into the tool Statistical Modeling and Estimation of Reliability Functions for Systems (SMERFS^3): • Conduct literature search (journals, conferences, 1990 up) • Select new models • Build new models into SMERFS^3 • Collect and organize data • Test new models with Goddard project data • Make latest version of SMERFS^3 available • CY’03: Software Reliability • CY’04: System Reliability / Availability SAS 04/ GSFC/SATC-NSWC-DD

  4. Importance / Benefits • Software Reliability Models • The Schneidewind risk assessment improvements add more “reliable” estimates to ALL the models • The hypergeometric has the promise of better estimates – need more data • The yield: better prediction of time to next failure, testing time needed, costs of testing • System Models • Measurement conducted either for hardware or for software • Total system failure and degraded mode of operation lead to availability measurement • The yield: repair time, time to failure, availability SAS 04/ GSFC/SATC-NSWC-DD

  5. Relevance to NASA • What do Space Station, Shuttle, the satellites, landers and rovers, science instruments, data management have in common? • Their missions rely on reliability and availability of large distributed systems! • Measurement of system availability and software reliability assists in: • Better test planning, schedule impact • Assessment of when to release • Establishing maintenance requirements SAS 04/ GSFC/SATC-NSWC-DD

  6. Accomplishments • Completed extensive literature searches • Implemented Schneidewind’s risk assessment improvements and hypergeometric model into SMERFS^3 • Tested SMERFS^3 with GSFC data and analyzed results • Completed report discussing new software reliability models, detailed mathematics, extensive analysis of application with GSFC data • Enhanced SMERFS^3 HELP and readme files • Identified major system reliability research, recognizing availability as an important additional attribute of systems • Identified key algorithms for availability • Acquired and prepared one set of data meeting data requirements for availability measurement SAS 04/ GSFC/SATC-NSWC-DD

  7. Accomplishments (Con’t) • Submitted paper to International Symposium on Software Reliability 2004 • Other applications • Applied Risk Assessment on a Joint DOD project (JEM) to assess feasibility of the stated software MTTF requirements for the system • Applied to Navy’s JWARN Mission Application Software to assess time to next Operational Mission Failure • Recognition • Invited to present software reliability seminar for medical device company (Wallace and Farr) • Invited to present at US Army Conference on Applied Statistics, October 2003 (Farr) SAS 04/ GSFC/SATC-NSWC-DD

  8. Next Steps • Identify and collect data from GSFC projects • Organize the data – usually a major task • Build availability model into SMERFS^3 • Exercise the new model with GSFC data • Report on the results SAS 04/ GSFC/SATC-NSWC-DD

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