However, data layering in eXpress goes beyond a simple layering and uses a special technique of abstraction so that changes to test and diagnostics approaches are somewhat resilient despite wide-sweeping design changes. It is this mechanism that allows assessment and optimization to occur throughout the entire design process.

To support the transition from early design studies through later full system integration, there is a crucial change that must take place in the design. Specifically, functions are slowly augmented with failure modes. At the early stages, functions form the connectivity and flow of the model, since that's what the system level design is comprised of. However, as the design matures, and subsystems enter the picture with increasing amounts of detail, failure modes become the data element upon which testing is often based.

How do you start by assessing functions and later assess failure modes without diverging from the original approach? eXpress provides the only hybrid modeling capability that allows this exact transition to occur at a testing level, without any loss of resolution or changes to the model. As failure modes are entered into the system, tests can be switched, on a component-by-component basis from functions to failure modes.

It is this ability to mesh functions with failure modes that brings eXpress to the earliest stages of development, without incurring a re-entry penalty later, as required by other approaches. In fact, the transition is so smooth, that the functions form the baseline upon which failure mode testing can be based. Of course, the final system testing concept will almost certainly rely on both functions and failure modes, so the functions in eXpress are not deleted--rather, they co-exist with failure modes for the life of the design.

IVHM, having such a system-wide impact, requires a sophisticated layering and abstraction approach to gathering information, to support the fast paced design environment that is created by this type of problem. eXpress, by having this type of problem factored from its beginnings as a design goal, achieves this through simple, object-oriented representation of component, function, failure mode and test data.

* Shrek is a registered trademark of DreamWorks LLC.