Software reuse in safety-critical airborne systems

Today no formal guidance or standards exist which maximizes the utility of software reuse in any industry. This is especially true in the development of safety-critical software. As a result, the embedded industry has been far from the goal of making reuse a standard practice in software development. A new policy issued by the Federal Aviation Administration (FAA) promises to create a major shift in how software is reused in safety-critical systems. A Reusable Software Components Advisory Circular published in December 2004, called AC 20-148, details the approach and documentation necessary for systematic reuse of software components that meet the guidelines of RTCA/DO178B. To fully appreciate the value of a reusable software component (RSC), one must understand the history of safety-critical software standards and development. A brief overview of safety-critical software development and the RTCA/DO- 178B standards is given as well as an overview of the Advisory Circular 20-148. A fully time and space partitioned operating system is used as an example in the paper.