mod_xhtml
mod_xhtml provides a namespace processor for
http://www.w3.org/1999/xhtml that serves to ensure XHTML meets the W3C
Appendix C guidelines for compatibility with HTML browsers and the
text/html MIME type. In addition, mod_xhtml implements Server Side
Includes (SSI), both as Apache's comment-driven processing language
and as a separate XML namespace processor.
SSI Implementation
The mod_xhtml SSI implementation is simpler than Apache's traditional
mod_include, in that it decouples the task of markup parsing from SSI
processing. Most importantly, as a namespace processor, it plugs
directly in to general XML-based publishing systems, without the
overhead of having to parse the markup twice.
mod_xhtml actually provides two ways to implement SSI:
1. Using traditional comments <!--#directive arg="val"-->
2. Using a separate namespace processor <ssi:directive arg="val"/>
The two are exactly equivalent and are implemented by the same code.
They can be enabled separately or mixed in a single document.
Limitations
The principal limitation in mod_xhtml is in what it works on. Unlike
mod_include, it requires its input to be well-formed XML, and cannot
be used on HTML4 or tagsoup input.
The SSI implementation is also incomplete:
* The SSI exec directive is deprecated in Apache, and not
implemented in mod_xhtml. This will probably never be implemented.
As in mod_include, include virtual is preferred.
* Regular expressions in expression matching are not supported. This
will probably be implemented sometime in future.
Acknowledgement
Much of the SSI implementation is based on mod_include, and mod_xhtml
includes a substantial amount of copied code.
Usage
As with any namespace module, using mod_xhtml is based on inserting
the xmlns filter from mod_xmlns or mod_publisher: e.g.
LoadModule xmlns_module modules/mod_xmlns.so
AddOutputFilter xmlns .html
or
LoadModule publisher_module modules/mod_publisher.so
AddOutputFilter markup-publisher .html
There are three namespace providers we can use, and several different
usages. Note that if you use mod_publisher, much of this is redundant,
and only the SSI namespace (the last example) provides functionality
over and above what's builtin.
1. To ensure Appendix C compliance without supporting SSI, insert the
basic provider for XHTML:
XMLNSUseNamespace http://www.w3.org/1999/xhtml on 1.0
2. To ensure Appendix C compliance and support classic SSI comments,
use the SSI-enabled namespace provider instead:
XMLNSUseNamespace http://www.w3.org/1999/xhtml on ssi
3. To ensure Appendix C compliance and support SSI as a namespace,
use the XHTML provider together with the SSI namespace provider:
XMLNSUseNamespace http://apache.webthing.com/ssi# on ssi
XMLNSUseNamespace http://www.w3.org/1999/xhtml on 1.0
4. To ensure Appendix C compliance and support SSI both as comments
and as a namespace (which may be freely mixed in a document)
XMLNSUseNamespace http://apache.webthing.com/ssi# on ssi
XMLNSUseNamespace http://www.w3.org/1999/xhtml on 1.0
5. To support the SSI namespace in XML-based publishing systems
without reference to XHTML, simply load the SSI namespace
provider:
XMLNSUseNamespace http://apache.webthing.com/ssi# on ssi
together with other namespace providers as required.
Configuration
mod_xhtml implements three configuration directives. These set
processing defaults that can be overridden in a document by the SSI
config directive. They all work as documented under mod_include's
config directive.
XHTMLSSIerrmsg
Sets the error message sent to the browser when a processing
directive fails.
XHTMLSSItimefmt
Sets the format for output of date/time fields.
XHTMLSSIsizefmt
Sets the format for output of size fields.
Availability
mod_xhtml is available under the GNU General Public License (GPL). As
with other opensource modules, alternative licenses may be considered
by request.
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