XML Processing Model Working Group Charter

The primary mission of the XML Processing Model Working Group, part of the Extensible Markup Language (XML) Activity, is to develop and maintain an XML-based pipeline language for orchestrating and specifying sequences and flows of operations to be performed upon XML documents.

Join the XML Processing Model Working Group.

End date 31 May 2015
Confidentiality Proceedings are public
Chair Norman Walsh
Team Contact
(FTE %: 5)
Liam Quin
Usual Meeting Schedule Teleconferences: Weekly as needed.
Face-to-face: TPAC plus 1-2 per year


The Working Group is hereby chartered to take XML processor profiles to Recommendation (in conjunction, if and as necessary, with the W3C TAG), and also to continue maintaining the First Version of XProc: An XML Pipeline Language.

The XML Processing Working Group, having successfully produced a first version of the XProc pipeline language, is hereby also chartered to work on the use cases and requirements for a second version of the XProc pipeline language. In addition, if this work should, in the opinion of the Working Group, entail the production of a Working Draft for a future version of the XProc language, such a Working Draft shall be deemed to be within the scope of this charter.

Liaison with the XSLT and XQuery Working Groups is to be encouraged, and the possibility of a Public Workshop is to be considered by the Working Group.

Success Criteria

The Working Group shall be considered a success if it has produced a Recommendation for XML processor profiles and also has produced requirements and use cases for a next version of XProc.

Out of Scope

Technical work on any Next Version of XProc beyond sketching out possible approaches is not in scope, because the Advisory Committee should be given an opportunity to comment on the magnitude and applicability of any proposed work, and also because a public call for participation for the work would be appropriate.


Other Deliverables

The Working Group will produce test suites for their specifications as needed to move through W3C Process and to promote interoperability.


Specification FPWD LC CR PR Rec
Note: The group will document significant changes from this initial schedule on the group home page.
Processor Profiles N/A N/A September 2013 November 2013 February 2014
XProc 2.0 Requirements and Use Cases October 2013 N/A N/A N/A N/A

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 XSLT 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 to be considered as a basis for future versions of the XProc language.

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 W3C XML Schema processing, and in particular with the Post-Schema Validation Information Set (PSVI) defined by the W3C XML Schema language.

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 [Member-only link].

Furthermore, XML Processing Model Working Group expects to follow these W3C Recommendations:


Participation is expected to consume up to one day per week of each participant’s time, and usually much less, 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.

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


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

This group primarily conducts its work on the public mailing list public-xml-processing-model-wg@w3.org (archive).

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

Decision Policy

As explained in the Process Document (section 3.3), this group will seek to make decisions when there is consensus. When the Chair puts a question and observes dissent, after due consideration of different opinions, the Chair should record a decision (possibly after a formal vote) and any objections, and move on.

This charter is written in accordance with Section 3.4, Votes of the W3C Process Document and includes no voting procedures beyond what the Process Document requires.

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 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.

This charter was revised to permit work on a new version of the primary deliverable, the XProc language, and to bring the end-date into line with other Working Groups within the XML Activity.

Charter author: Liam R. E. Quin

$Date: 2013-07-23 16:38:09 $