Element Domain Specialization Step 4: Integrate The Module Into a Document Type Shell
Step 4-4. Update Type-Specific Parameter Entities in Shell DTD
Step 4-6. Include .mod Declaration Set

Step 4-5. Update @domains attribute with new domain

Add the XML domain to the @domains attribute declaration. In concept.dtd, find the comment that says "DOMAINS ATTRIBUTE OVERRIDE". Update the &included-domains; entity declaration to include the &xml-d-att; text entity: 
<!ENTITY included-domains 
   "&hi-d-att; 
    &ut-d-att; 
    &xml-d-att; 
   "                
>

Note that your &included-domains; value may be different. The example shows the value used for the concept shell used by this tutorial's topics, which includes only the highlight and utility domains.