Re: 2167A Questions

[psinntp!vitro.com!news@uunet.uu.net (Morris J. Zwick)]

In article <1993Jul21.142339.20342@schbbs.mot.com> tannen@tigger.geg.mot.com
(David Tannen) writes:
>When working in 2167A I have tried to organize system in the following manner:
>
>	CSU = package (ie Unit test is @ the package level)
>	CSC = subsystem(s) There can be multiple layers of CSCs if you want.
>	CSCI = whole system (all the CSCs)
>
>For instance:
>	Your system will have three different pieces of hardware (A,B,C) and 
>	the system is called XYZ.
>
>	Subdivide the system as so:
>		XYZ CSCI
>		A CSC
>		B CSC
>		C CSC
>

I'm not sure I agree with this. Typically, CSCI's are determined to be
"autonomous" systems or subsystems. Code running on each piece of hardware can
generally be considered as separate subsystems. Perhaps my disagreement further
highlights some of the problems with 2167A.

I'll try a different example. Say we have some weapons control system with two
computers, A&B. Let's say that computer A contains subsystems to track the
target(a), determine if we can shoot at the target(b), and tell the equipment
to do something about it(c). Let's say computer B contains subsystems to accept
sensor data (d) and control display devices (e).

First, the CSUs in the system are represented by each procedure, function, or
package in the system. This is the easiest part. Let's say in computer A, CSU's
(a1),(a2),(a3),and(a4) concern tracking the target, (b1),(b2), and (b3) concern
determining if we can shoot at the target, etc. In this (very) simplistic case,
I would say that (a),(b),(c),(d),and(e) are all CSCs, and CSC (a) has component
CSUs (a1),(a2),(a3),and(a4), CSC (b) has component CSUs (b1),(b2),and(b3), etc.
Last, depending on the designers, we COULD have CSCIs A and B, where CSCI A is
called something like Target Tracking and Scheduling Subsystem and CSCI B is
Sensor Data and Display Subsystem. CSCI A would be composed of CSCs (a), (b),
and (c) and CSCI B would be composed of CSCs (d) and (e).

Of course, in a real system we would probably have many more lower-level CSCs
and the highest level CSCs, (a) and (b) for example, would be made up of other
CSCs. However, you get the idea. The whole purpose of the exercise is to
decompose the system into manageable components. There is no "right" way to do
this for any given system. That's why they pay us the big bucks ;)

Hope this helps,
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