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<!--#set var="revision" value="\$Id: devel.html,v 1.6 2002-08-20 01:51:24 link Exp $"
--><!--#set var="date" value="\$Date: 2002-08-20 01:51:24 $"
--><!--#set var="title" value="Developer Documentation for The W3C HTML Validation Service"
--><!--#set var="relroot" value="../"
--><!--#include virtual="../header.html" -->
<p id="skip">
The W3C HTML Validation Service consists of an SGML Parser, an SGML
catalog, a CGI program and it's configuration files. In addition it
relies on a moderately large set of Perl modules for it's operation.
</p>
<p>
This document tries to draw a roadmap of the prerequisits and what the
different parts of the system do. It is intended for system
administrators and people interested in helping developing the validator.
This is not end user documentation. See the
<a href="users.html">User Manual</a> for usage instructions.
</p>
<div id="prereq" class="stb">
<h2>Prerequisites</h2>
<p>
Apart from a properly configured web server, the Validator needs a
SGML parser -- that does all the heard work -- and several Perl
modules used by the "check" CGI script.
</p>
<p>
The SGML parser we're currently using is "lq-nsgmls", which is <a
href="http://www.jclark.com/">James Clark</a>'s
<a href="http://www.jclark.com/sp/">SP</a> with patches from Liam Quinn.
</p>
<p>
In the future we may switch to a different parser to improve error
reporting and XML support.
<a href="http://OpenJade.sourceforge.net/">OpenSP</a> from the OpenJade
team springs to mind.
</p>
<p>
The canonical list of Perl modules we use can be found in the source
for the "check" CGI script. There is a bunch of lines that of the form
"use Foo::Bar" where each "Foo::Bar" represents a module. Most modules
can be found on <a href="http://www.cpan.org/">CPAN</a>. The following
list was complete when CVS spit out: <code>$Date: 2002-08-20 01:51:24 $</code>. <tt>:-)</tt>
</p>
<dl>
<dt><code>LWP::UserAgent</code></dt>
<dd>
Gisle Aas« most excellent WWW library for Perl. This is where our
support for downloading pages off the net comes from.
</dd>
<dt><code>URI::Escape</code></dt>
<dd>Module to handle escaping special characters in URIs</dd>
<dt><code>CGI::Carp</code></dt>
<dd>CGI-aware warn()/die()</dd>
<dt><code>CGI</code></dt>
<dd>
The all-singing, all-dancing,
everything-<em>and</em>-the-kitchen-sink, Perl CGI library. This
takes care of all those niggly little bits of CGI for us and make
options parsing and file upload a breeze.
</dd>
<dt><code>Text::Wrap</code></dt>
<dd>Wrap text to a sane width. Needed for source output in results.</dd>
<dt><code>Text::Iconv</code></dt>
<dd>
Perl-native interface to the (g)libc iconv(3) library. Handles
charset conversion issues.
</dd>
</dl>
</div>
<div id="config" class="stb">
<h2>Configuration Files</h2>
<p>
The validator uses a number of configuration files -- most of which
are really mapping tables of some form -- to avoid having to check in
a new version of the code every time a new version of HTML comes out.
All configuration files can be found in
<code>$CVSROOT/validator/htdocs/config/</code>.
</p>
<p>
To really understand what each does you should read the source, but
here is a short description to get you started.
</p>
<dl>
<dt>eref.cfg</dt>
<dd>
Contains the mappings from element names to an URI fragment
(relative to a configurable URI) for their definitions. Used
in output when the "Show Source Input" option is enabled.
</dd>
<dt>fpis.cfg</dt>
<dd>
Maps FPIs to plain text version strings.
</dd>
<dt>frag.cfg</dt>
<dd>
Maps error messages to an URI fragment identifier where an
explanation of that error can be found. Currently not used and may
be phased out in the future (to be replaced with a more robust
system).
</dd>
<dt>type.cfg</dt>
<dd>
Maps MIME/HTTP Content-Types to an internal "document type" which
is used for treating HTML, XML, and XHTML in different ways.
</dd>
<dt>check.cfg</dt>
<dd>
Main configuration file. Gives various parameters (such as the
address of the maintainer and the URL for the "Home Page") and
the locations of the other configuration files and mapping tables.
</dd>
</dl>
</div>
<div id="todo" class="stb">
<h2>TODO</h2>
<p>
The TODO list for the Validator is online at
<URL:<a href="../todo.html">http://validator.w3.org/todo.html</a>>.
This is probably the best place to start.
</p>
<p>
However this list is by no means comprehensive. Feel free to suggest
other features that should be on this list or send patches for your
favourite feature.
</p>
<p>
Keep in mind that features should be of general utility and that the
point if the validator is that it does an <em>objective</em>
validation instead of just what some random developer happens to
think is a Good Idea®. While extra features are nice, they
shouldn't dilute the value of the validator as an objective check.
</p>
</div>
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