Element Domain Specialization Step 3: Declare The Module Entities File
Step 3-1. Create xmlDomain.ent
Step 3-3. Declare Domain Usage Text Entity

Step 3-2. Declare Type-Specific Integration Entities

Declare a type-specific entity for the keyword-based elements, listing all the element types in the module: 
<!-- ====================================================
     XML Construct Domain Module
    
     Author: your name here

     Copyright (c) 2011 copyright holder
     
     license to use or not use or whatever
          
     ==================================================== -->

<!ENTITY % xml-d-keyword
  "xmlelem | 
   xmlatt | 
   textent | 
   parment |
   numcharref
  "                 
  >