Re: Use of XML for config files

[Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>]

Ted Dennison <dennison@telepath.com> wrote:
: What's wrong is:
: 
: 1) It could be *far* smaller than that, if we were parsing a simpler
: syntax.

far by what amount?
<item key="the_key">value string of some average length</item>
the_key:=value string of some average length

2/3.

: <item><key>...</key></item> all the time, if *everything* is an item,
: and key is the only attribute we ever use?

If this is so, well...
You mention real time systems, but I wonder whether a configuration
for an AWS application will get anything but messy if it has to
be configured with key value pairs only. Ada equivalent: put everything
in one big package.

I don't understand this verbosity and design aversion in an Ada context :-)

: I will cost us, in that it will make the file much harder for humans
: to read.

Depends. (On the design of the (implicit or explicit) DTD.
Of course, with XML being for computers, SGML with all its
tag omission features etc. being for humans, this is to be expected,
at least if there isn't a decent design.)

: I'm particuarly thinking of the site maintanence engineers

who could use _any_ XML enabled editing tool to write valid
configuration files (where valid refers to XML validation).

: as its easy to forget an end tag or
: transpose a letter somewhere.

the idea behind XML is that you don't have to write tags yourself.
That would be the province of the XML application (e.g. editor) or
of full SGML, where, e.g. an HTML like list can look like

<ul>
<li>bla
<>the
<>foo
</ul>

instead of XML's

<ul>
<li>bla</li>
<li>the</li>
<li>foo</li>
</ul>

Admittedly, it is _really_ sad that so many XML data floating
around make a bad impression by not making use of valuable
XML features.  Builtin cross referencing, element _types_
with _constraint_ checking, etc.

: You really whould have trouble doing that if your only syntax is "=".

True,  but how does this brevity stop you from making typing
errors? How do you check the correctness of the configuration?
Where are the namespaces? You would have to search back to the
latest section heading or

namespace.key=value
manespace.kez=valeur  -- 3 typos, not easily noted!


: if we are getting something back that we can't get out of
: a more simple configuration file format.

An annotated typed tree is different from a flat anything-list.
I think it depends on the application whether a list of a few
settings like in environment variables is sufficient or not.

Should the decision between very simple Key(i) = value(i)
and a grammar driven externally checked configuration be frozen
in the API?


-- georg