Overriding an XSLT-processing step

You can override specific XSLT-processing steps in both the pre-processing pipeline and certain DITA-OT transformations.

Develop an XSL file that contains the XSL override.
Construct a plugin.xml file that contains the following content:
```
<?xml version="1.0" encoding="UTF-8"?>
<plugin id="*plugin-id*">
  <feature extension="*extension-point*" file="*relative-path*"/>
</plugin>
```
where:
- plugin-id is the plug-in identifier, for example, com.example.brandheader.
- extension-point is the DITA-OT extension point, for example,dita.xsl.xhtml. This indicates the DITA-OT processing step that the XSL override applies to.
- relative-path is the relative path and name of the XSLT file, for example, xsl/header.xsl.
Use the dita install subcommand to install the plug-in.

Note: For more information, see Installing plug-ins.

The plug-in installer adds an XSL import statement to the default DITA-OT code, so that the XSL override becomes part of the normal build.

Example: Overriding XHTML header processing

The following two files represent a complete, simple style plug-in.

The plugin.xml file declares an XSLT file that extends XHTML processing:

<?xml version="1.0" encoding="UTF-8"?>
<plugin id="com.example.brandheader">
  <feature extension="dita.xsl.xhtml" file="xsl/header.xsl"/>
</plugin>

The xsl/header.xsl XSLT file referenced in plugin.xml overrides the default header processing to add a banner:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template name="gen-user-header">
    <div><img src="http://www.example.com/company_banner.jpg" 
              alt="Example Company Banner"/></div>
  </xsl:template>
</xsl:stylesheet>

Related information

XSLT-import extension points

Installing plug-ins

DITA-OT mdBook Demo

Overriding an XSLT-processing step

Example: Overriding XHTML header processing