Development Assurance process integral processes

The SwS development assurance and integrity process is based on a stringent set of LOR tasks, which when successfully completed increase the confidence that ... 

Conclusion. Successful implementation of a sustainable development mindset in an organization requires true integration of the values and principles behind sustainability, and not a shallow, cursory, stand-alone project. That is, sustainability is only one small piece of a larger approach to organizational responsibility in the global environment. The audit or assurance process is an important and valuable step in this approach that cannot and should not be overlooked. 

Software reliability assessment is different from traditional reliability techniques and requires a different process. The use of development standards is common in current good practice. Software safety standards recommend processes to design and assure the integrity of safety-related software. However the reasoning on the validity of these processes is complex and opaque. 

Change Safety Analysis and Risk Assessment Process is the part of the overall Engineering Safety and Assurance Process (ESAP). The author developed ESAP as a generic System Integration process. For clarity, firstly the ESAP will be depicted and, following on from there, details of the Change Safety Analysis and Risk Assessment Process will be provided. 

Systemic failures are due to human errors (e.g. mistakes, misconceptions, miscommunications, omissions) in the specification, design, build, operation and/or maintenance of the system. Errors in this case are taken to include both mistakes and omissions. Errors can be introduced during any part of the lifecycle and errors are caused by failures in design, manufacture, installation or maintenance. Systematic failures occur whenever a set of particular conditions is met and are therefore repeatable (i.e. items subjected to the same set of conditions will fail consistently) and thus apply to both hardware and software. It is difficult to quantify the rate at which systemic failures will occur and a qualitative figure based on the robustness of the development/build process is normally used. The probability of systemic failures is often evaluated by means of safety integrity (or development assurance) levels. 

It is almost impossible to test complex software fully - even if it is run many times - as there are an almost infinite number of possible loops, variables and subroutines that may or may not be run in any single program. Program operation is by its very nature non-linear or non-determined and therefore can never be fully tested at box level. For these reasons, reliability calculations are not applied to software, as it has no MTBF. Instead, we make use of development assurance levels (DAL) or safety integrity levels (SIL) (see Table B.6). The main aim or purpose of DALs and SILs is to introduce a number of repeatable life-cycle processes which (if used by the developer) will produce a final product that is capable of meeting not only the original specification requirements, but also producing the correct level of safety both for the developed equipment and the overall aircraft. 

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