ENHANCED CONDITION TABLES FOR VERIFICATION OF FAULT TOLERANT SOFTWARE

THE GOAL OF THE RESEARCH IS TO DEVELOP A FEASIBLE, CREDIBLE, AND THOROUGH VERIFICATION METHODOLOGY FOR FAULT TOLERANT SOFTWARE AND TO DEVELOP THE TOOLS THAT WILL MAKE ITECONOMICALLY FEASIBLE FOR SYSTEM DEVELOPERS, IV&V CONTRACTORS, AND GOVERNMENT USERS. AN IMPLICIT ASSUMPTION IN THE RESEARCH COMMUNITY IS THAT EXISTING VERIFICATION TECHNIQUES COULD SOMEHOW BE ADOPTED. HOWEVER, FAULT TOLERANT SOFTWARE POSES A UNIQUE VERIFICATION PROBLEM: ENSURING THAT THE HARD CORE IS ERROR FREE UNDER ALL ANTICIPATED EXECUTION STATES. THE HARD CORE IS THAT PORTIONOF THE FAULT TOLERANT SOFTWARE WHICH IS NOT REDUNDANT AND WHICH MUST EXECUTE PROPERLY EACH TIME IT IS INVOKED. THE ACCEPTANCE TEST IN A RECOVERY BLOCK IS AN EXAMPLE. SOHAR PREVIOUSLY DEVELOPED A VERIFICATION TECHNIQUE FOR HARD CORES CALLED THE ENHANCED CONDITION TABLE (ECT). THE PROPOSED RESEARCH WILL INVESTIGATE THE FEASIBILITY OF THE ECT FOR LARGER DEVELOPMENT EFFORTS BY EXERCISING IT ON A PORTION OF A FAULT TOLERANT DISTRIBUTED NUCLEAR REACTOR CONTROL SYSTEM NOW BEING DEVELOPED BY OUR COMPANY. THE EFFORT IS OF INTEREST TO ALL NASA SPACE MISSIONS.