Equivalence of document-type shells

Two distinct DITA document types that are taken from different tools or environments might be functionally equivalent.

A DITA document type is defined by the following:

  • The set of vocabulary and element-configuration modules (constraint and expansion) that are integrated by the document-type shell
  • The values of the @class attributes of all the elements in the document
  • Rules for topic nesting

Two document-type shells define the same DITA document type if they integrate identical vocabulary modules, element-configuration modules (constraint and expansion), and rules for topic nesting. For example, a document-type shell that is an unmodified copy of the OASIS-provided document-type shell for topic defines the same DITA document type as the original document-type shell. However, the new document-type shell has the following differences:

  • It is a distinct file that is stored in a different location.
  • It has a distinct system identifier.
  • If it has a public identifier, the public identifier is unique.
Note (non-normative):
The public or system identifier that is associated with a given document-type shell is not necessarily distinguishing. Two different people or groups might use the same modules and constraints to assemble equivalent document-type shells, while giving them different names or public identifiers.