With the increasing emphasis on utilizing existing technology as much as possible, we have recently seen a shift towards the use of Commercial Off The Shelf (COTS) products. In fact, virtually all DoD contracts today call for COTS components as the first choice for design wherever practical and to the extent that they meet specified requirements. The objective is, of course, to make development and production more affordable-a goal that, at first glance, would appear to be unequivocally admirable. Unfortunately, prescribing this "pill" could do you more harm than good if it was not expressly intended for system use. Quick solutions to lowering development costs may, from an ownership (customer) standpoint, result in even more costly support scenarios. Our goal is to shed some light on this hasty and often unnecessary practice and to help reduce the total costs of development, production and support.System performance, as defined in DoD Directive 5000.2, "Defense Acquisition Program Procedures" is composed of not only operational characteristics but support characteristics as well. DoD 5000.2 (Para. C.. DEFINITIONS, 7. Performance.) further states that "The support characteristics of the system include both supportability aspects of the design and the support elements necessary for system operation." Often, this co-performance support angle is overlooked in favor of immediate cost-cutting measures that can be more quickly realized during the operational portion of the design equation. In today's competitive environment, it is too often a consideration to cut design costs at the expense of diagnostic effectiveness; even though the out-briefing of the "Desert Storm" conflict recognized that more and better diagnostics are essential to success in the modern battlefield.
COTS components, more often than not, lack the necessary diagnostic hooks. LSI components often lack the fault coverage required to satisfy the high percentage fault detection or isolation requirements demanded by modern systemsætypically in the realm of 95% detection of Mission Critical failures. Let's not forget that the use of COTS implies, by definition, a bottom-up methodology of designing. It may successfully "fit the bill" operationally, but could easily fall short in the system diagnostics and support arena. The areas in which the benefits of COTS are most often realized are those efforts which are price-conscious, short-term and multi-application. This is typically the case when a simple generic alternative is sought. What must never be overlooked, however, is that the systems integrator is ultimately accountable for any support deficiencies-as well as a host of other costly related liabilities-and taking the wrong pill could result in disastrous side-effects.
The use of COTS produces becomes a far more viable alternative when it is incorporated into a top-down systems diagnostics development process. The primary objective should be to determine all the necessary functional allocations and the access that would be required for effective diagnostics before the system is synthesized into the hardware design. Ideally, one would like to know complete system and environmental diagnostic information before the functionality of the system is validated (frozen). This can only be achieved when the system diagnostic requirements and overall diagnostic strategy provide a basis for determining what types of diagnostic hooks are needed from the COTS components. Implementing a top-down diagnostic/operational co-development process that is targeted towards system diagnostics can yield a system which is truly a support jewel.