Improving Software Quality Using FMEA and FTA Defect Prevention Techniques in Design Phase

The cost of finding and correcting defects represents one of the most expensive software development activities. And that too, if the errors get carried away till the final acceptance testing stage of the project life cycle, then the project is at a greater risk in terms of its Time and Cost factors. A small amount of effort spent on quality assurance will see good amount of cost savings in terms of detecting and eliminating the defects. The purpose of defect prevention is to identify those defects in the beginning of the life cycle and prevent them from recurring so that the defect may not surface again. Software for safety-critical systems must deal with the hazards identified by safety analysis in order to make the system safe, risk-free and fail-safe. Certain faults in critical systems can result in catastrophic consequences such as death, injury or environmental harm. The focus of this paper is an approach to software safety analysis based on a combination of two existing fault removal techniques. A comprehensive software safety analysis involving a combination of Design Failure Modes and Effects Analysis (DFMEA) and Design Fault Tree Analysis (DFTA) is conducted on the functions of the critical system during design phase to identify potentially hazardous design faults. A prototype safety-critical system Elevator Door Control System (EDCS), is described here and DFMEA and DFTA technique is applied on a component of EDCS. Keywords—Defect, Defect Analysis, Defect Prevention, Root Cause Analysis software safety, safety-critical systems, DFMEA, DFTA