Rules for document-type shells

This topic collects the rules that concern DITA document-type shells.

XML grammars

While the DITA specification only defines coding requirements for DTD and RELAX NG, conforming DITA documents MAY use other document-type constraint languages, such as XSD or Schematron.

Defining element or attribute types
With two exceptions, a document-type shell MUST NOT directly define element or attribute types; it only includes vocabulary and element-configuration modules (constraint and expansion). The exceptions to this rule are the following:
  • The ditabase document-type shell directly defines the <dita> element.
  • RNG-based document-type shells directly specify values for the @specializations attribute. These values reflect the details of the attribute domains that are integrated by the document-type shell.
Document-type shells not provided by OASIS

Document-type shells that are not provided by OASIS MUST have a unique public identifier, if public identifiers are used.

Document-type shells that are not provided by OASIS MUST NOT indicate OASIS as the owner. The public identifier or URN for such document-type shells SHOULD reflect the owner or creator of the document-type shell.

For example, if creates a copy of the document-type shell for topic, an appropriate public identifier would be "-//EXAMPLE//DTD DITA Topic//EN", where "EXAMPLE" is the component of the public identifier that identifies the owner. An appropriate URN would be