Charter of the XML Processing Model Working Group

Norman Walsh, Mark Logic Corporation, Chair
Liam Quin, Team Contact

The XML Processing Model Working Group is a Working Group of the W3C and follows the Working Group process described in section 6.2 Working Groups and Interest Groups of the Process Document.


The XML Specification defines an interchange format for structured information, but does not define how that format is to be used. Other specifications, such as XSLT, XML Schema, XInclude and XML Canonicalization define transformations that operate on and produce XML documents. The order in which these transformations are to be applied is not specified anywhere, even though applying them in different orders will in general yield different results.

The XML Processing Model Working Group has defined a language for expressing pipelines of cooperating processes, XProc, an XML Pipeline Language. During this charter period, the XML Processing Model Woking Group will process errata on that document, and may also gather requirements and use cases for a future version.

In addition, the XML Processing Model Working Group has explored whether an XML-based system can determine whether the creator of any given XML document has indicated that operations on that document should be performed in a specific order for a particular result, and if so, how to apply those operations. This might take the form of reference to an external document in the XML Processing language, or some form of annotation regarding the self-describing aspects of the document. There is however no expectation that all documents will provide either form of indication, nor is there any expectation that such an XML Processing model as the WG produces will be the only way anyone will process XML documents. The Working Group has published a draft of XML processor profiles to reflect this work, and expects to take it to a W3C Recommendation.


The goals of the XML Processing Model Working Group are to develop and maintain two Recommendation Track documents, and to consider future work.

There may also be a public Workshop to be held in conjunction with other Groups in the area of future work, and in particular the development of large applications using XProc, XQuery, XSLT and related technologies..


  1. XProc, an XML Pipeline Language (maintain and consider future work)
  2. XML processor profiles (complete and publish as Recommendation; maintain as necessary)


The current work of the Group is expected to be completed during this chartered period; if future work is identified, such as a new version of the Pipeline language, the Group will be rechrtered to reflect the necessary resources.


Specification FPWD LC CR PR Rec
Note: The group will document significant changes from this initial schedule on the group home page.
XProc Model Requirements March 2011 N/A N/A N/A N/A
Processor Profiles N/A December 2010 March 2011 June 2011 August 2011

Timeline View Summary


The expiration date of this charter is 31 January 2012.

Relationship with Other Activities

The XSL Working Group

XSLT is a commonly used transformation mechanism, and XSL-FO a frequent (and the original intended) target of such transformations.

The XML Query Working Group

The XML Query Language can be used to select data from arbitrary collections of XQuery 1.0 and XPath 2.0 Data Model instances; the XQuery 1.0 and XPath 2.0 Data Model specification is maintained jointly by the XSL and XML Query Working Groups, and is a possible starting point for an XML Processing Model.

The XML Schema Working Group

A W3C XML Schema document can provide default document content which could (for example by introducing XInclude directives or default attribute values) substantially affect the results of other transformations.

The XML Processing Model must interact in a well-defined manner with the PSVI.

The XML Core Working Group

The XML Processing Model Specification was originally within the scope of the XML Core Working Group, and was taken out for logistical reasons.

Interactions with core specifications such as xml:base and XInclude must be carefully reviewed.

The Technical Architecture Group

The work on default behaviors for the XML Processing Model will need coordination with the TAG. The XML Processing Model should also be aligned with the Web Architecture, including the role of Internet media types.

Formal liaison between the XML Processing Model Working Group and other W3C Working Groups, as well as organizations outside of the W3C, shall normally be accomplished through the XML Coordination Group.

Working Group Participation

Participation is expected to consume up to half a day per week of each participant’s time, although the time commitment for the chair and editors may be higher.

The level of participation expected for this Working Group suggests that representatives be experts in the development and use of XML-related specifications, as well as being W3C Members or Invited Experts.


The initial Chair of the XML Processing Model Working Group is Norman Walsh.

W3C Team resources

The initial Team Contact will be Liam Quin (5% FTE).


The Working Group generally has bi-weekly teleconferences. Face-to-face meetings will be held as needed.


The XML Processing Model Working Group shall communicate among its participants using the public-xml-processing-model-wg publicly-readable mailing list and with the other XML Working Groups through the w3c-xml-plenary mailing list. Both lists are archived.

Public comment on the work of the XML Processing Model Working Group may be submitted via the public-xml-processing-model-comments public mailing list.


The proceedings of this working group are publicly readable, subject to exceptions made by the chair. In particular, the archive of the mailing list used for technical discussion and the Group home page are publicly readable.

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.

How to Join the Working Group

Information about how to join the Working Group is available on a separate “How-to-Join page”.

About this Charter

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

Please also see the previous charter for this group.

The 2011 revisoin of this charter introduces no Recommendation Track deliverables.

Liam Quin, XML Activity Lead
Last modified $Date: 2011/04/12 21:57:55 $