Step 4-4. Update Type-Specific Parameter Entities in Shell DTD

Add the module type-specific parameter entities to the domain extension parameter entities. In concept.dtd, find the comment that says "DOMAIN EXTENSIONS". Update the %keyword; parameter entity declaration to include the %xml-d-keyword; parameter entity:
<!ENTITY % keyword
  "keyword |

This declaration has the effect of including all the XML module's keyword-type elements wherever keyword is allowed in the base DITA-defined content models.