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The DocBook Schema Version 5.1b1

Editor's Draft

23 June 2010

Technical Committee:
OASIS DocBook Technical Committee
Norman Walsh, MarkLogic Corporation
Norman Walsh, MarkLogic Corporation
Declared XML Namespace:



DocBook is a general purpose [XML] schema particularly well suited to books and papers about computer hardware and software (though it is by no means limited to these applications).

The Technical Committee provides the DocBook 5.1 schema in other schema languages, including W3C XML Schema and an XML DTD, but the RELAX NG Schema is now the normative schema.


This is a Editor's Draft. It does not necessarily represent the consensus of the committee.

Please send comments on this specification to the list. To subscribe, please use the OASIS Subscription Manager.


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Table of Contents

1. Introduction
1.1. Terminology
1.2. Normative References
1.3. Non-Normative References
2. The DocBook RELAX NG Schema
3. Identifying DocBook Documents and Schemas
4. Conformance
5. Backwards compatibility
6. Release Notes
6.1. Backwards Incompatible Changes Planned for DocBook V6.0
A. The DocBook Media Type
A.1. Registration of MIME media type application/docbook+xml
A.2. Fragment Identifiers
B. Acknowledgements
C. Revision History

1. Introduction

DocBook is general purpose XML schema particularly well suited to books and papers about computer hardware and software (though it is by no means limited to these applications).

The DocBook Technical Committee maintains the DocBook schema. Starting with V5.0, DocBook is normatively available as a [RELAX NG] Schema (with some additional [Schematron] assertions). W3C XML Schema and Document Type Definition (DTD) versions are also available.

The Version 5.1 release adds a major new feature to DocBook: the ability to compose document assemblies specifically designed to be suitable for use in topic-based authoring methodologies. It also adds a topic element, in support of topic-based authoring, and fixes a small number of bugs.

The DocBook Technical Committee welcomes bug reports and requests for enhancement (RFEs) from the user community. The current list of outstanding requests is available through the SourceForge tracker interface. This is also the preferred mechanism for submitting new requests.

1.1. Terminology

1.1.1. Key words

The key words must, must not, required, shall, shall not, should, should not, recommended, may, and optional in this Editor's Draft are to be interpreted as described in [RFC 2119]. Note that for reasons of style, these words are not capitalized in this document.

1.2. Normative References

[XML] Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, et. al., editors. Extensible Markup Language (XML) 1.0 (Fifth Edition). World Wide Web Consortium. 26 November 2008.

[XLink11] Steven DeRose, Eve Maler, David Orchard, Norman Walsh, editors. XML Linking Language (XLink) Version 1.1. World Wide Web Consortium, 2005.

[W3C XML Datatypes] Paul V. Biron and Ashok Malhotra, editors. XML Schema Part 2: Datatypes. World Wide Web Consortium, 2000.

[RELAX NG] ISO/IEC JTC 1, SC 34. ISO 19757-2:2008(E) Information technology — Document Schema Definition Language (DSDL) — Part 2: Regular-grammare-based validation — RELAX NG. 2008.

[Schematron] ISO/IEC JTC 1, SC 34. ISO 19757-3:2006(E) Information technology — Document Schema Definition Languages (DSDL) — Part 3: Rule-based validation — Schematron. 2006.

[RFC 2119] IETF (Internet Engineering Task Force). RFC 2119: Key words for use in RFCs to Indicate Requirement Levels. S. Bradner. 1997.

[RFC 3023] IETF (Internet Engineering Task Force). RFC 3023: XML Media Types. M. Murata, S. St. Laurent, D. Kohn. 2001.

[DocBook: TDG5] Norman Walsh and Leonard Meullner. DocBook 5.0: The Definitive Guide.

1.3. Non-Normative References

[SGML] ISO/IEC JTC 1, SC 34. ISO 8879:1986 Information processing -- Text and office systems -- Standard Generalized Markup Language (SGML). 1986.

[W3C XML Schema] Henry S. Thompson, David Beech, Murray Maloney, et. al., editors. XML Schema Part 1: Structures. World Wide Web Consortium, 2000.

2. The DocBook RELAX NG Schema

Summary of changes in 5.1 TBD.

Requests for enhancement addressed by this release:

  • RFE 1679665 Add better support for modular documentation

  • RFE 1722935 Add a proofreader value to the class attribute for othercredit

  • RFE 1770787 Add givenname as an alternative for firstname

  • RFE 1899655 Allow more elements to be the root of a DocBook document

  • RFE 2100736 Allow constant in initializer

  • RFE 2791288 Added several additional elements, including quote, to the ubiquitous inlines

  • RFE 2820190 Add a topic element

  • RFE 2821653 Remove the constraint that indexterm elements must not appear in footnotes

  • RFE 2907124 Allow personal name components directly in bibliomset.

  • RFE 2907125 Allow all inlines in remark

  • RFE 2907131 Allow simplesect in colophon

  • RFE 2964576 Fix the bug that allowed table to appear inside entry

3. Identifying DocBook Documents and Schemas

Historically, when DocBook was defined by a DTD, DocBook documents could be identified by the presence of standard public and/or system identifiers in the document type declaration. RELAX NG, the normative schema language for DocBook V5.1, does not provide any equivalent mechanism.

For systems that can make use of public identifiers, e.g., systems where the informative DTD is being used, the following public identifier can be used for DocBook V5.1: “-//OASIS//DTD DocBook V5.1//EN//XML”.

4. Conformance

This specification normatively defines DocBook V5.1 with a RELAX NG grammar and a set of Schematron assertions. A conformant DocBook V5.1 document must be valid according to both the grammar and the assertions.

The reference documentation describes additional constraints and processing expectations. A conformant DocBook V5.1 document should respect those constraints and anticipate those processing expectations.

5. Backwards compatibility

The DocBook Technical Committee understands that the community benefits from the long-term stability of the DocBook family of schemas. We also understand that DocBook must continue to adapt and change in order to remain relevant in a changing world.

All changes, and especially changes that are backwards incompatible (changes that make a currently valid document no longer valid under a new version of the schema), have a cost associated with them. Our duty is to balance those costs against the need to remain responsive to the community's desire to see DocBook grow to cover the new use cases that inevitably arise in documentation.

With that in mind, the DocBook Technical Committee has adopted the following policy on backwards incompatible changes. This policy spells out when backwards incompatible changes can occur and how much notice the TC must provide before adopting a schema that is backwards incompatible with the current release.

This policy allows DocBook to continue to change and adapt while simultaneously guaranteeing that existing users will have sufficient advance notice to develop reasonable migration plans.

With respect to schema changes, the following points must always apply:

  1. A point release (X.1 to X.2, X.2 to X.3, X.1 to X.1.2, etc.) must not contain any backwards incompatible changes unless those changes correct obvious bugs accidentally introduced in the preceding version.

  2. A major release (X.1 to Y.0, X.2 to Y.0, X.1.2 to Y.0, etc.) may contain backwards incompatible changes if both of the following conditions are true:

    • The change was announced in the release notes for the previous version (major or minor).

    • The change was announced in a release that occurred at least six months previously.

By these rules, the TC can announce, in V5.1 for example, its plans to make a backwards incompatible change in V6.0. Then, in V6.0, if it's been at least six months since V5.1 was released, it can make that change.

The exclusion in point 1 is designed to allow the committee to correct errors accidentally introduced in a point release, that are technically backwards incompatible, without having to leave them in the schema until the next full version.

6. Release Notes

See http://www.relaxng.org/ for a list of tools that can validate an XML document using RELAX NG. Note that not all products are capable of evaluating the Schematron assertions in the schema.

6.1. Backwards Incompatible Changes Planned for DocBook V6.0

The following backwards incompatible changes are planned for DocBook V6.0:

  1. The linking elements will be removed from the content model of biblioid.

  2. The common linking attributes will be removed from indexterm.

  3. The xml:id attribute will be made required on startofrange indexterms.

  4. A Schematron constraint will be added to assert that for every startofrange indexterm there is exactly one endofrange indexterm that points to it.

  5. The language attribute will be removed from address; use xml:lang instead.

A. The DocBook Media Type

This appendix registers a new MIME media type, “application/docbook+xml”.

A.1. Registration of MIME media type application/docbook+xml

MIME media type name:


MIME subtype name:


Required parameters:


Optional parameters:

This parameter has identical semantics to the charset parameter of the application/xml media type as specified in [RFC 3023] or its successors.

Encoding considerations:

By virtue of DocBook XML content being XML, it has the same considerations when sent as “application/docbook+xml” as does XML. See [RFC 3023], Section 3.2.

Security considerations:

Several DocBook elements may refer to arbitrary URIs. In this case, the security issues of RFC 2396, section 7, should be considered.

Interoperability considerations:


Published specification:

This media type registration is for DocBook documents as described by [DocBook: TDG5].

Applications which use this media type:

There is no experimental, vendor specific, or personal tree predecessor to “application/docbook+xml”, reflecting the fact that no applications currently recognize it. This new type is being registered in order to allow for the deployment of DocBook on the World Wide Web, as a first class XML application.

Additional information:
Magic number(s):

There is no single initial octet sequence that is always present in DocBook documents.

File extension(s):

DocBook documents are most often identified with the extension “.xml”.

Macintosh File Type Code(s):


Person & email address to contact for further information:

Norman Walsh, .

Intended usage:


Author/Change controller:

The DocBook specification is a work product of the DocBook Technical Committee at OASIS.

A.2. Fragment Identifiers

For documents labeled as “application/docbook+xml”, the fragment identifier notation is exactly that for “application/xml”, as specified in [RFC 3023] or its successors.

B. Acknowledgements (Non-Normative)

The following individuals have participated in the creation of this specification and are gratefully acknowledged:

  • Gary Cornelius, Individual
  • Paul Grosso, Arbortext
  • Dick Hamilton, Individual
  • Nancy Harrison, IBM
  • Scott Hudson, Individual
  • Gershon Joseph, Tech-Tav Documentation Ltd.
  • Jirka Kosek, Individual
  • Larry Rowland, Hewlett-Packard
  • Robert Stayton, Individual (Secretary)
  • Norman Walsh, MarkLogic Corporation (Chair, Editor)

C. Revision History

This specification does not yet reflect any schema changes.