SVID changes

[Doug Gwyn]

For the benefit of those whose knowledge about the SVID is limited
to what they read in this newsgroup, let me clarify a few points.

So far as I am aware, there have been two "issues" of the SVID.  An
"issue" basically obsoletes the previous issue.

However, an Issue in general consists of an open-ended set of
individual Volumes published at different times.  So far I have
three Volumes in Issue 2 of the SVID.  Volumes 1 & 2 basically
supplanted, then extended, what was in SVID Issue 1.  Volume 3
contains interface specs for features introduced after UNIX System
V Release 2, plus a few revisions to specs in the earlier volumes.
In general, revisions extend the functionality without changing it,
or correct technical errors in earlier specs.  There have been few
significant changes to the interfaces specified in earlier issues/
volumes of the SVID, which is as one would expect -- large changes
would cause trouble for existing applications, and riling existing
customers is no way to keep their business.  For the most part,
each new volume has merely introduced additional functionality.

The SVID was designed to provide for controlled evolution of the
specs, which is necessary to correct problems and track future
developments.  (The alternative, a "stagnant standard", is of
comparatively little value.)  The rule was, an impending change
would be pre-announced at least three years in advance, and would
be flagged in the SVID as such.  For example, from the beginning
the UNIX "plot" and PWB/Graphics functionality was flagged as
obsolescent.  (In this particular case, no replacement has appeared!)
I'm not sure the 3-year rule has been strictly followed in recent
volumes..

Of course, the SVID development has gotten somewhat screwed up by
the recent independent development of UNIX "standards" which AT&T
will pretty much have to accommodate somehow.  For example, there
will have to be a considerable revision of the SVID for POSIX
compatibility.  I don't know if AT&T is planning on starting a new
"issue" for that or adding another volume to Issue 2.