The purpose of making the source code available is partly to allow others to set up mirrors of the service (either publicly or within an intranet behind a firewall), but also to allow us to collaborate on making the service better -- there are many ways the service could be improved!

Retrieving the Code

You can retrieve the code a number of ways:

If you just want to glance at the code, or see its revision history, you can browse it on the web.

The most interesting files are currently a CGI script called "check" that does pretty much everything, and possibly also the httpd.conf. (Select the topmost revision numbers on these pages to see the most recent revision of each file.)
If you want a copy of all the files that make up the service, you can grab a tar ball (~2.8MB).
If you intend to actively mirror the code and/or contribute patches to the code, you should install and become familiar with CVS; this is the tool we use for revision control and is generally a good thing to get to know. More information on CVS is available courtesy of Pascal Molli.

Our CVS base is available read-only, using CVS pserver authentication a la:
```
    bash$ export CVSROOT=":pserver:anonymous@dev.w3.org:/sources/public"
    bash$ cvs login
    (Logging in to anonymous@dev.w3.org)
    CVS password: anonymous
    bash$ cvs get validator
    cvs server: Updating validator
    cvs server: Updating validator/htdocs
    U validator/htdocs/about.html
    ...
          
```

Prerequisites

Before you will be able to get the code to run, you will need a few things already installed on your system:

A Unix-like operating system. It may also work with Windows NT, Mac OS X or other systems. It has worked on Linux, Solaris, FreeBSD, HP-UX, and Digital UNIX. If you try it on other systems and get it to work, please let us know (and send us patches, if they are needed to get it to work elsewhere).
OpenSP, version 1.5 or newer. OpenSP is the SGML and XML parser used by the service.
A collection of DTDs and other files to validate against. (You do not need to download this if you mirror everything using CVS.)
A web server: we are currently running Apache version 1.3.27, but likely any version will work, and other web servers may work as well with some tweaking. In particular, the server needs to be able to run CGI scripts and have support for SSI.
Perl: the main CGI script that does everything is written in Perl. You'll need version 5.6.0 or newer. Additionally, the following CPAN distributions are needed:
- CGI.pm, version 2.81 or newer
- Config-General, version 2.06 or newer
- HTML-Parser, version 3.25 or newer
- libwww-perl, version 5.60 or newer
- Set-IntSpan
- Text-Iconv
- URI

If you try to use the code and succeed (or fail), please let us know!

Development

For information on current development activity, see the www-validator mailing list archives. To join in discussions about the Validator, please join us in the #validator IRC channel on irc.freenode.net.

Any changes to the service will attempt to maintain compatibility with a list of test cases. Any changes to the code or documentation related to the service cause a notification message to be sent to the www-validator-cvs mailing list.