A DITA specialization includes:
A specialization can be integrated in Oxygen XML Author with minimum effort.
If the DTD's that define the extension elements are located in a folder outside the DITA Open Toolkit folder you should add new rules to the DITA OT catalog file for resolving the DTD references from the DITA files that use the specialized elements to that folder. This allows correct resolution of DTD references to your local DTD files and is needed for both validation and transformation of the DITA maps or topics. The DITA OT catalog file is called catalog-dita.xml and is located in the root folder of the DITA Open Toolkit.
If there is specialized processing provided by XSLT stylesheets that override the default stylesheets from DITA OT these new stylesheets must be called from the Ant build scripts of DITA OT.