ETTC'2003 - SEE

lifetimes within a single system. The main tools are the workflow, which still has a
serial character, and the digital technical data management that abandons paper in
favor of digital means, but without changing the underlying processes;
• with the explosion of new information technologies, the sequential character has
vanished in the late 90’s, and has been replaced by concurrent and integrated
processes, where shared repositories and reuse within and between domains
become the major issues. The PDM (“product design management”), and PLM
(“product lifecycle management”) processes organize work and bring the
necessary dynamic and flexible feature to promote efficiency and reactivity.
In order to mirror such transformations, which have been under way among the
industrial contractors, and which go much further than a mere change of working tools, it is
crucial for the stakeholders to adopt new practices that also favor such a change. If acquisition
methods do not evolve, the stakeholders cannot take advantage of the major savings
performed by the contractors, and cannot control risks and costs as it should be possible: a coevolution
is necessary, as similar methods, tools and collaborative working system
engineering environments have to be used.
Test and simulation throughout the life-cycle of a system
The integrated approach between tests and simulation should be applied as early as
possible: from the preparation phase of a new program, before the design of the system. Be it
to identify and represent threat issues, general operational employ concepts, or to write down
the operational requirements, different types of simulations can be very useful.
During the design of the system, the same happens, to explicit the functional
requirements and the technical specifications. Risks levees can be conducted easily by using
adequately simulations coupled with functional tests. The first elements of the virtual
prototype are then available; they rely on the traceability between requirements and
specifications, and establish consistency between the logical, functional and physical views of
the system. Such a consistency, and its justification via the joint use of simulations and trias is
essential. From it comes the possibility of running impact analyses: when modifying an
element of one of the views (for instance a requirement, or a function, or a component) it is
possible (ideally easy) to evaluate the implications at the system level, and it is possible to
identify the necessary new validations (via tests or simulations) that guarantee there is no
regression in terms of system performance.
Let us underline that such a capacity is essential, since it explains many cost drifts in
programs. The complimentary feature of tests and simulations appears here: whereas the
initial test has allowed to fit correctly the simulation within explicit and traced validity
conditions, the non-regression test can be run through simulation with a reliable and estimable
credibility. The cost and time saving are immediate and justify the idea of running simulations
and tests together within an engineering system process.
Such a joint use of simulations and tests allows to switch from a “test, correction, test”
approach to an iterative and incremental approach “model, simulation, correction, test”. The
latter allows correction at each phase of the lifecycle and updating of the model when
necessary. Such a correction is done at the model level or on the virtual prototype: money and
time are saved. Such a model can also been used subsequently to predict and extrapolate the
possession cost, to evaluate the technical and operational performance, the system
availability…