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The Benefit of a Systems Approach
By Andy Medwell, Purple Secure Systems


“Modern defence procurements are greatly dependent on a wide range of sophisticated software; this technology provides an increasingly high proportion of the military capability afforded by contemporary defence systems. The characteristics of these software-enabled systems and their interactions with the systems of systems within which they are deployed are many and complex; their development requires a high degree of engineering competence.”

“This article discusses the benefits to defence primes, systems integrators and software systems developers of engaging both systems engineers with a strong software engineering background, and software engineers with an appreciation of systems engineering, in the development of complex defence systems.”


Typical defence system procurements have a high dependency on a wide range of sophisticated software technology. Software has provided an increasingly high proportion of the military capability afforded by contemporary defence systems for some time; for example, both Typhoon and the Joint Combat Aircraft have 80-90% of their functions enabled by software1 and this trend is set to continue.

Software is as ubiquitous within modern defence systems as it is complex. It is well understood that if end-user requirements are to be fulfilled within acceptable commercial boundaries significant engineering effort and skill at the systems level is required.

Within the software community many of the activities, methodologies and approaches used have evolved from, or have analogues in, the systems domain. More recently, developments within the software community have been appropriated by systems engineers: examples include the evolution of the Systems Modelling Language (SysML) from the Unified Modelling Language (UML) and Rational Unified Process for Systems Engineering (RUP SE) from RUP.

It is clear that engineers with an understanding of both software and systems engineering can make a vital contribution to the successful development of software intensive defence systems; this article develops this idea by examining the relationship between software and systems engineering and the benefits to the defence sector that may be obtained from the cross-fertilisation of the two.
Defence Systems Engineering

Systems engineering in the defence sector has a broad scope; it governs both the fundamental activities of the engineering lifecycle and provides the coordinative processes that must occur to create a system. Broadly speaking, systems operating in the defence domain are socio-technical systems, and therefore the engineering specialities, training, logistics and support also fall within the systems domain.

A number of constraints, peculiar to the defence sector, add further complexity to the way in which systems development must take place. The nature of the relationship between industry, the MoD customer and the end-user means that requirements are often fluid and may evolve during the development lifecycle. Frequently, development will be disturbed by an Urgent Operational Requirement (there have been more than 1800 in the five years since Op Telic 1).

Defence systems engineering processes are strongly informed by MoD procurement policy, the Acquisition Operating Framework and CADMID; the engineering model must be aligned with the current (and evolving) capability based acquisition process. It must also provide for incremental development and continual through-life technology refresh. It must encompass all Defence Lines of Development and may need to co-exist with other architectural views and within systems frameworks, particularly the MoD Architecture Framework (MoDAF).

Extensive commercial and legal limitations will impact the engineering solution: the intricacies of the relationships between integrators and consortiums of primes, I

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