Repository feature proposal

[Konstantin Riabitsev]

On Sun, 2003-10-19 at 12:24, Nicolas Mailhot wrote:
> Sure - however xml is getting more prevalent and even if it's not the
> easiest format to grok for a human it's always easier than learn
> yet-another-config-file format.

Win-ini style config is really easy to learn and edit:

[section]
variable = value

> Really if one doesn't forget to put comments in the file, use strict dtd
> checks so the app can tell on startup what errors were made, does not
> forget to indent properly its file and uses a logical namespace xml can
> be a joy to read. People do forget xml "verbosity" is here to help human
> readers.

There are several significant drawbacks to using xml for config files.
Here is an incomplete list:

1. Having to escape values.
<foo>
  You have to make sure that all <, >, & and " characters
  are escaped, otherwise your config file will break. Reading content 
  with escaped characters is NOT easy or simple, or obvious. 
  Alternatively, one must use <![CDATA[Even less obvious "CDATA" 
  constructs, which allow <>&, but are questionably better]]>
</foo>

2. Having to watch your comments.
<!-- <foo>
 This section has been commented out and is fine.
</foo> -->

<!-- <foo>
 <!-- This section does foo -->
 This section has been commented out, but is illegal, because it has a
 nested comment inside.
</foo> -->

<!-- <foo>
 This section has been commented out, but it is illegal -- it has a 
 double dash in it, which is not allowed inside a comment.
</foo> -->

It is very important for a sysadmin to be able to comment out parts of
some config files. It quickly becomes very irritating if they have to
constantly make sure that there are no nested comments inside these
config files, or that there are no double dashes used anywhere.

3. Keeping your DTD/Schema definitions current quickly becomes a burden.
You can't just add a new configuration directive -- if your app relies
on DTD checking for validity, you then have to edit your DTD.

My rule has been:
1. If the config file can be expressed in simple section/variable/value
pairs, then use win.ini-style config files. They are easy to read, easy
to edit, and they don't require extra effort to keep valid. If, however,
that is not sufficient to express your config, then use XML. Let's face
it -- most config data is just assigning values to variables, and for
that XML is an overkill. 

Regards,
-- 
Konstantin Riabitsev <icon at linux.duke.edu>
Linux at DUKE