Date: Tue, 27 Mar 2001 09:57:59 -0800 From: Jack Rusher <jar@integratus.com> To: "freebsd-arch@FreeBSD.ORG" <freebsd-arch@FreeBSD.ORG> Subject: Re: configuration files, XML? Message-ID: <3AC0D4A7.CF09E4A3@integratus.com> References: <200103270707.f2R77SR08693@cwsys.cwsent.com>
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Cy Schubert - ITSD Open Systems Group wrote:
>
> around the bush. What specifically are you proposing? What would
This is a mass reply. I will now address the following:
o What's the problem?
Unix file formats have traditionally been created in an ad hoc
fashion in whatever format the author of that subsystem felt like. This
leads to a seemingly random collection of position dependent, tagged,
and line oriented file formats.
The authors of the subsystems in question were likely to repeat the
same set of parser errors with every subsystem. Steve Johnson's lex &
yacc have made common input handling mistakes less frequent, but not
everyone uses that technology. And, even if they DO use lex/yacc, it's
so flexible that configuration file formats still remain random.
Unix file formats don't contain self descriptive metadata (some
people say "holographic labels"). This context information is really
helpful in preventing people from making silly mistakes whilst editing
these files.
There is no constraint language for most configuration files. This
makes it hard to write programs that can edit these files. You would
essentially need to write one custom program for each format to make
this work. This sucks for several reasons: sysinstall is harder to
write & maintain, a "system configurator" is a big pain in the ass, and
writing a netconfigd that allows machines to be reconfigured from the
network is an artificially harder problem.
There are more, but that seems like enough.
o How does this relate to AIX?
The point of this little project isn't to produce IBM's SMIT for
BSD. Someone can write a SMIT if they feel that it'll make the end user
experience more pleasant. The real point is that you've got a platform
on which to write such a beast, or anything else that programmatically
mucks with system configuration. I'm sure Son of Sysinstall would like
this functionality.
o What do you want to do about it?
What I would like to see is a set of constraint files that describe
the syntax of configuration files on the system, a consistent "style"
for these file formats, and an API to access a library that knows how to
deal with the underlying files. I would suggest that the library
support loadable file format modules and that a hacked up constraint
language that's able to express current file formats is the first module
we write. After we have that much done, some enterprising soul could go
around and retrofit this configuration file library into existing
applications and subsystems.
Note: at this point no user has experienced a user interface change.
After we have all of this done, new applications and subsystems can
code to the new API and avoid the common mistakes mentioned above & we
can start experimenting with different back ends (XML, whatever) using
an /etc/conf.conf approach. If we pull off the library correctly, we
get conversion betwixt file formats pretty cheaply.
Thanks,
--
Jack Rusher, Senior Engineer | mailto:jar@integratus.com
Integratus, Inc. | http://www.integratus.com
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