Re: Tools vs. Parts

[jimmaureenrogers@worldnet.att.net (Jim Rogers)]

Wesley Groleau <wesgroleau@despammed.com> wrote in message news:<6LidnfIK-pvMZjqjXTWcog@gbronline.com>...
> A little imagination and analogy:
> 
[snip]
> (I could drag this on for a long time .....)
> 
> I'm sure we all get the point, no matter which
> side of personality spectrum we're on.  But
> just in case someone needs a hint, look at the
> initials of all the names.
> 
> (or make up an acronym for "carb off the shelf")


The old "buy or build" issue has been around for a long time.
In recent years the issue has become more important to U.S. 
Department of Defense projects because the Government officials
have legislated the use of Commercial Off The Shelf products to
save cost. The decision logic assumes that a product good enough
for industry is good enough for the military.

In some cases the logic holds, and COTS products are appropriate.

There are other cases where the logic fails dramatically.
COTS hardware has never been built to the usage specifications 
required by the military. These specifications include a very wide
range of temperatures, humidity, and altitude. They also include
resistance to shock and vibration beyond commercial standards.
Finally, military equipment must be sealed against NBC exposure.
(NBC stands for Nuclear, Biological, and Chemical).

COTS software is very useful when used the same way it is in 
industry. COTS software is inappropriate in mission critical
systems. Military systems tend to have lifetimes counted in
decades, while commercial software tends to have lifetimes 
counted in months. This means that a military system built 
upon COTS software will be unsupported by the vendor within
18 to 24 months, while it must continue to operate for 30
years.

COTS products also present a major challenge in reliability
predictions. Few commercial vendors will share reliability
data about their products, if they even keep such data. One of the
factors that should be used to choose between COTS and custom
products is reliability. A cheap initial COTS purchase may result
in high maintenance and risk costs if it exhibits low reliability.
Conversely, an expensive initial purchase of a custom product
with high reliability can result in a low overall cost of 
ownership.

Jim Rogers