.\"
.\"	aegis - project change supervisor
.\"	Copyright (C) 1991, 1992, 1993 Peter Miller.
.\"	All rights reserved.
.\"
.\"	This program is free software; you can redistribute it and/or modify
.\"	it under the terms of the GNU General Public License as published by
.\"	the Free Software Foundation; either version 2 of the License, or
.\"	(at your option) any later version.
.\"
.\"	This program is distributed in the hope that it will be useful,
.\"	but WITHOUT ANY WARRANTY; without even the implied warranty of
.\"	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\"	GNU General Public License for more details.
.\"
.\"	You should have received a copy of the GNU General Public License
.\"	along with this program; if not, write to the Free Software
.\"	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
.\"
.\" MANIFEST: User Guide, Introduction, Why use aegis?
.\"
.nh 2 "Why use aegis?"
.LP
So why should you use the aegis program?
The aegis program uses a particular model of the development of software
projects.
This model has a master source (or baseline) of a project,
consisting of several (possibly several hundred) files,
and a team of developers creating changes to be made to this baseline.
When a change is complete,
it is integrated with the baseline,
to become  the new baseline.
Each change must be atomic and self-contained,
no change is allowed to cause the baseline to cease to work.
"Working" is defined as passing its own tests.
The tests are considered part of the baseline.
Aegis provides support for the developer so that an entire copy of
the baseline need not be taken to change a few files,
only those files which are to be changed need to be copied.
.LP
The win in using the aegis program is that there are
.I O(n)
interactions between developers and the baseline.
Contrast this with a master source which is
being edited directly by the developers - there is
.I O(n!)
interactions between developers - this
makes adding "just one" more developer a potential disaster.
.LP
Another win is that the project baseline always works.
Always having a working baseline means that a version is always available for
demonstrations,
or those "pre-release snapshots" we are always forced to provide.
.LP
The above advantages are all very well - for management types.
Why should Joe Average Programmer use the aegis program?
Recall that RCS provides file locking,
but only for one file at a time.
The aegis program provides the file locking, atomically, for the set of files
in the change.
Recall also that correct RCS usage locks the file the instant you start
editing it.
This makes popular files a project bottleneck.
The aegis program allows concurrent editing,
and a resolution mechanism just before the change must be integrated,
meaning fewer delays for J.A.Programmer.