Starting with DITA-OT 1.5.4, you can use the plugin:plugin-id URI extension and the ${dita.plugin.plugin-id.dir} Ant variable to reference the base path of another
    installed DITA-OT plug-in.
    
      Sometimes you need to reference content in another DITA-OT plug-in. However, the path to an installed plug-in
        is not guaranteed to be the same between different installed instances of DITA-OT. The plugin:plugin-id URI extension and ${dita.plugin.plugin-id.dir} Ant variable are provided so your build and XSLT files always
        use the correct path to the plug-in.
      Within a single plug-in, you can safely use relative path references, for example,
          xsl/my.xsl without specifying the path to the plug-in itself.
    
    Procedure
- 
        Use ${dita.plugin.plugin-id.dir} in Ant build files.
        
          Use the Ant variable ${dita.plugin.plugin-id.dir} anywhere in your build file or
            template to point to the base path of an installed DITA-OT plug-in. 
 
          The following example copies CSS files from the HTML5 plug-in: <copy todir="${dita.temp.dir}/css">
  <fileset dir="${dita.plugin.org.dita.html5.dir}/css" 
           includes="*.css"/>
</copy>
 
 
- 
        Use plugin:plugin-id in XSLT files.
        
          Use the URI extension plugin:plugin-id at the beginning of a
            file reference—usually in <xsl:import>—to point to the base path of an installed
            DITA-OT plug-in.
 
 
          The following example imports the base output-message.xsl processing: <xsl:import href="plugin:org.dita.base:xsl/common/output-message.xsl"/>
 
 
          To use the URI extension, your plug-in must reference the DITA-OT catalog file. In your Ant build file, add
            an <xmlcatalog>element referencing the DITA-OT catalog file as a child of the<xslt>element.
 
 
          <xslt style="xsl/my.xsl"
      in="${dita.temp.dir}/input.file" 
      out="${dita.temp.dir}/output.file">
  <xmlcatalog refid="dita.catalog"/>
</xslt>
 
 
For both of these methods, make sure you use the plug-in ID (defined in the plugin.xml
        file) rather than the folder name of the plug-in. In many cases, the folder name is not the same as the plug-in
        ID.