XML Companion, The, Third Edition

Document modelling

As with many other adjunct standards, inclusion markup may need to be added to an existing DTD or XML Schema model.

The appropriate markup for inclusion of the Include to a DTD is as follows:

<!ELEMENT xi:include EMPTY>
<!ATTLIST xi:include
          xmlns:xi       CDATA          #FIXED
                         "http://www.w3.org/2001/XInclude"
          href           CDATA          #REQUIRED
          parse          (xml|text)     "xml"
          encoding       CDATA          #IMPLIED>

Note that the default value for the Parse attribute is 'xml', though this is not strictly necessary because a missing Parse attribute is assumed to indicate this mode in any case. This attribute need not be defined at all, if the 'text' mode is not applicable to the application of XML concerned. At the other extreme, however, this attribute could also be defaulted ...