Schemas for DocBook V5.0 are available in several formats at http://www.oasis-open.org/docbook/xml/5.0/ (or the mirror at http://docbook.org/xml/5.0/). Only the RELAX NG schema is normative, and it is preferred over the other schema languages. For your convenience there are also DTD and W3C XML Schema versions provided for DocBook V5.0. However, neither the DTD nor the W3C XML schema can capture all the constraints of DocBook V5.0. This means that a document that validates against the DTD or XML schema is not necessarily valid against the RELAX NG schema, and thus may not be a valid DocBook V5.0 document.
DTD and W3C XML Schema versions of the DocBook V5.0 grammar are provided as a convenience for users who want to use DocBook V5.0 with legacy tools that don’t support RELAX NG. Authors are encouraged to switch to RELAX NG-based tools as soon as possible, or at least to validate documents against the RELAX NG schema before further processing.
Some document constraints can’t be expressed in grammar-based schema languages like RELAX NG or W3C XML Schema. To define these additional constraints DocBook V5.0 uses Schematron. We recommend that you validate your document against both the RELAX NG and Schematron schemas.
The latest versions of schemas can be obtained from http://docbook.org/schemas/5x.html. At the time this was written the latest version was 5.0. Individual schemas are available at the following locations:
These schemas are also available from the mirror at http://www.oasis-open.org/docbook/xml/5.0/.