ARINC-653 - ACHIEVING SOFTWARE REUSE

A key goal of the ARINC 653 (APEX) specification is the achievement of software re-use through provision of a standard operating environment for applications software. Reuse of software can be achieved in two w ays: (i) by re-using operating systems, which provide common functions across the application spectrum, eg. health monitoring, process manag ement, communications mechanisms; and (ii) by re-using the application s software which provides avionics applications functions. By provisio n of a standardised interface between applications and operating syste m, ARINC 653 facilitates both forms of re-use. Operating systems are b y nature tightly coupled to the underlying hardware platform, re-use o f operating systems is therefore limited to modules employing the same hardware unless a new standard such as COEX (Core Executive Interface ) can be tightly defined. Applications software is often dependent on the actual aircraft implementation. Direct re-use of applications will not always be possible; however, by use of ARINC 653, it will be poss ible to re-use individual partitions of an application in other applic ations. ARINC 653 is language-dependent and within languages such as A da there is scope for functionally identical implementations which are syntactically different. Unless definitive language implementations o f ARINC 653 are adhered to, language issues will become a major hurdle to re-use. A large cost of avionics development (particularly softwar e) is the cost of certification. Currently, avionics functions are cer tified at the 'system' level. In order to maximise the benefits of sof tware re-use, means must be found to claim credit for previously-devel oped software components of a system, EUROCAE WG48 and RTCA SC182 are currently investigating this issue in their definition of an Avionics Computing Resource. It is hoped that these groups, working in co-opera tion with ARINC 653, will provide the means to achieve the benefits of re-use.