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XML Schema Working Group Charter

The mission of the XML Schema Working Group, part of the Extensible Markup Language (XML) Activity, is to maintain and enhance the XML Schema Definition Language, an XML vocabulary for defining document classes by specifying structural and non-structural constraints on documents. XML Schema is similar to, but more expressive than, the notation given in XML 1.0 and SGML for document type definitions.

Join the XML Schema Working Group.

End date 31 January 2011
Confidentiality Proceedings are Member-only
Initial Chair David Ezell
Initial Team Contacts
(FTE %: 25)
Henry S. Thompson
Usual Meeting Schedule Telcons: Weekly
Ftf: 3 to 4 per year


The XML Schema Working Group is in the process of finishing publication and review of an updated version of XML Schema Definition Language, called XSD 1.1. This new version has many new features of importance to users in industry and in other standards efforts that require the specification of XML languages. The primary focus of the Working Group is to move this new version toward Recommendation Status and to maintain it and older versions of XSD, including XML Schema 1.0.

Success Criteria

The Working Group expects to demonstrate at least 2 interoperable implementations of all required and optional features of XSD 1.1 before requesting to advance to Proposed Recommendation.


A set of W3C Recommendations for:

XSD 1.1 implements many features and also fixes bugs in XML Schema 1.0. The Component Designators document has been written to support either XSD 1.1 or XML Schema 1.0.

Other Deliverables

The following additional items will be developed and/or maintained by the XML Schema Working Group:

  • An interoperability test suite for XSD 1.1: intended to assess the accuracy of the Candidate Recommendation, and to promote interoperability.
  • Errata list for XML Schema version 1.0 and XSD 1.1, with new editions of the 1.0 and 1.1 specification as needed
  • Errata list for XML Schema Component Designators, with new additions of the specification as needed
  • A documented set of features and capabilities that the Working Group believes to be essential for the next generation XML Schema Definition Language
  • A Working Group note on how to implement versioning using XSD 1.1

The following additional items may be developed and/or maintained by the XML Schema Working Group:

  • A Working Group note on simplified syntax for XSD 1.1
  • An updated version of the XML Schema Primer [Part 0] for use with XSD 1.1


Specification FPWD LC CR PR Rec
XSD 1.1 Part 1: Structures N/A December 2008 February 2009 June 2009 August 2009
XSD 1.1 Part 2: Datatypes N/A December 2008 February 2009 June 2009 August 2009
XSD: Component Designators N/A December 2008 March 2009 December 2009 February 2010
XSD 1.1 Part 0: Primer August 2009 October 2009 January 2010 April 2010 May 2010

Timeline View Summary


The expiration date of this charter is 30 November 2010.


W3C Groups

XML has become a strategic technology in W3C and elsewhere. The deliverables of the XML Schema Working Group must satisfy the dependencies from other W3C Working Groups. Some dependencies to and from other W3C Working Groups will require close cooperation during the development process; history has shown that the requirements posed for the Schema work by these Working Groups may change substantially during the development process, which means the interdependency of the Schema work with these Working Groups must be managed actively:

XML Query Working Group
The XML Query Working Group expects to use schema-related information in the processing of queries; we will discuss points of mutual interest in an effort to ensure that XML Schema provides the information Query needs. In particular, the XML Query Working Group has expressed particular interest in the definition of the post-schema-validation infoset (PSVI). The XML Schema Working Group will continue to collaborate with XML Query and XSL in work on operators for XML Schema datatypes and (as appropriate) on the integration of support for the XML Schema type inventory into future versions of XPath. An important goal of XML Schema 1.1 will be to align its type system more fully with the needs of the XML Query language and related specifications. Work on XQuery 1.1, updates, and full-text search may raise schema-related problems, and the Working Groups will cooperate in resolving them.
XSL Working Group
In collaboration with the XML Query Working Group, the XSL Working Group expects to make future versions of XPath and XSLT support schema-related information, specifically type information. The XML Schema Working Group will continue to collaborate with XML Query and XSL in work on operators for XML Schema datatypes and (as appropriate) on the integration of support for the XML Schema type inventory into future versions of XPath. An important goal of XML Schema 1.1 will be to align its type system more fully with the needs of the XSLT and XPath 2.0 languages and related specifications.
Service Modeling Language (SML) Working Group
The XML Schema WG intends to continue to work closely with SML. Several new features of XSD 1.1 accomodate (in part) requirements raised by SML. The XML Schema WG intendes to continue to support the current and future versions of SML.
XHTML Working Group
It is a goal of the XML Schema work to ensure that the structural schema language we define will suffice for the requirements of current versions of the XHTML specification.
XML Core Working Group
The XML Schema work defines methods for specifying constraints on XML documents; those constraints should apply to objects and properties identified as significant by the XML Information Set specification.The XML structural schema specification uses namespaces to combine fragmentary structural specifications; it also defines schema-validation for documents using namespaces. (In short: the XML Schema work is namespace-aware.)
Internationalization Working Group
Since XML Schema is expected to be an important tool for the definition of markup vocabularies, it may have follow-on effects on a larger number of people than create XML Schema documents directly. The XML Schema Working Group and the Internationalization Working Group will work together to clarify and resolve internationalization and localization issues in XML Schema, and will jointly ensure that it satisfies W3C goals for international access to the Web.
Web Services Working Groups
XML Protocol and Web Services Description Language specified in the Web Services Activity use XML Schema extensively. The XML Schema Patterns for Databinding Working Group is working to produce specifications to ease interoperability in Web Services where XML Schema is involved. The XML Schema Working Group will ensure that the schema language is sufficient to meet the requirements of deliverables from these Web Services Working Groups. The XML Schema Working Group will also discuss points of mutual interest and will review deliverables from the Web Services Working Groups and provide them with feedback.

Some other work groups should be mentioned here; there are no requirements for co-development of features with these Working Groups, but there are points of contact between their work and that of this Working Group, and thus logical dependency between their deliverables and those of this Working Group. Requirements from these Working Groups are expected to be well suited for communication via documents.

WAI Protocols & Formats Working Group
Reuse of common constructs greatly facilitates accessibility; the WAI PF Working Group will review work on structural schemas to be sure cost/benefit design decisions are informed of the benefits of accessibility.
OWL Working Group
Though no formal requirement for collaboration has been stated, the requirements posed by the OWL working group with regard to designating semantics, especially in datatypes, will undoubtedly gain focus during ongoing publication of XML Schema 1.1 and subsequent errata consideration.

When approved by the XML Coordination Group, liaison with other W3C Working Groups can be accomplished through joint task forces. It is expected that such task forces may be required for liaison with at least the XML Query, XSL and Internationalization Working Groups.


To be successful, the XML Schema Working Group is expected to have 5 or more active participants for its duration. Effective participation to XML Schema Working Group is expected to consume half of a work day per week for each participant; two days per week for editors. The XML Schema Working Group will allocate also the necessary resources for building Test Suites for each specification.

Participants are reminded of the Good Standing requirements of the W3C Process.


This group primarily conducts its work on the Member-only mailing list w3c-xml-schema-ig@w3.org (archive), as well as various other lists: w3c-xml-schema-wg@w3.org (archive). Public feedback for publication happens through www-xml-schema-comments@w3.org (archive), and general questions about the language come through xmlschema-dev@w3.org (archive).

Information about the group (deliverables, participants, face-to-face meetings, teleconferences, etc.) is available from the XML Schema Working Group home page.

Patent Policy

This Working Group operates under the W3C Patent Policy (5 February 2004 Version). To promote the widest adoption of Web standards, W3C seeks to issue Recommendations that can be implemented, according to this policy, on a Royalty-Free basis.

For more information about disclosure obligations for this group, please see the W3C Patent Policy Implementation.

About this Charter

This charter for the XML Schema Working Group has been created according to section 6.2 of the Process Document. In the event of a conflict between the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Please also see the previous charter for this group.

Liam Quin, XML Activity Lead
Henry Thompson, Staff Contact

$Date: 2009/02/11 22:52:05 $