W3C Architecture Domain | XML | Member-Confidential!

XML Query Working Group Charter

April 2002

Paul Cotton (Microsoft), chair
Massimo Marchiori (W3C/MIT), staff contact
last revised at $Date: Tuesday 11 May 2004 - 04:15:26 $ by $Author: massimo $.
revision history

The XML Query Working Group is a Working Group of the W3C and follows the working group process described in the Process Document. Except as outlined elsewhere in this charter, the Working Group follows the Common Procedures for XML Working Groups. This is an extension of the charter for this Working Group.  It extends the Working Group's previous charter [Member-only link] until September 2003 when the XML Activity Charter expires.


  1. Scope
  2. Deliverables and Schedule
  3. Relationship with Other Activities
  4. WG membership and decision process
  5. Communication
  6. W3C staff resource commitment


The mission of the XML Query working group is to provide flexible query facilities to extract data from real and virtual documents on the Web.  Real documents are documents authored in XML. Virtual documents are the contents of databases or other persistent storage that are viewed as XML via a mapping mechanism.

The functionality of the XML Query language would encompass selecting whole documents or components of documents based on specified selection criteria as well as constructing XML documents from selected components.

Features already designed within DOM, XSLT, and XPointer, and related specifications provide mechanisms for specifying locations/addresses, for tree traversal, and so forth in an XML document.  A current challenge, arguably, is to unify some of these expression/querying sub-languages as a basis for building generalized query facilities that are applicable to a broad range of requirements within different user communities.

The goal of the XML Query Working Group is to produce a formal data model for XML documents with Namespaces (based on the XML Infoset), a set of query operators on that data model (a so-called algebra), and then a query language with a concrete canonical syntax based on the proposed operators.  According to W3C guidelines, such syntax should be expressed in XML. The queries allowed by the query language must be computable and terminating. Such queries will act on fixed collections of XML documents.

In building such an XML data model, operators and query language, the working group will take into account the papers and proposals presented at the W3C Query Languages Workshop (QL'98).

The XML Query Working Group is part of the W3C XML Activity.

Deliverables and Schedule

These are subject to revision due to editorial needs and external scheduling issues; updates will be negotiated with the related groups and recorded on the XML Query WG home page.

April 2002

Publication of Working Drafts

Extension of Charter announced

May 2002

F2F meeting at a location to be determined.

July 2002

F2F meeting at a location to be determined.

Aug 2002

Publication of Last Call Working Drafts

Oct 2002

F2F meeting at a location to be determined.

Oct 2002

Publication of Candidate Recommendation Working Drafts.

Dec 2002

F2F meeting at a location to be determined.

Jan 2003

Publication of Proposed Recommendations.

February 2003

F2F meeting at a location to be determined.

April 2003

Publication of XML Query 1.0 Recommendation

F2F meeting at a location to be determined.

July 2003

F2F meeting at a location to be determined.

The expected duration of the working group under this charter is through September 2003 when the current XML Activity charter expires.

The XML Query Working Group has prepared distinct initial working drafts for a) the XML Query Data Model, b) XML Query Formal Semantics (Algebra), c) the XQuery 1.0 specification, d) the XQueryX specification and e) the XQuery Functions and Operators specification.  It is not yet clear whether these five Working Drafts should form five distinct Recommendations, or be merged into a single Recommendation; this question will be decided when the Last Call Working Drafts are released.

After making significant progress on XML Query 1.0, the XML Query WG is chartered to investigate extending XQuery 1.0 with additional facilities which might include: a) an update language, b) a grouping facility, etc. This work will involve publishing a new Requirements document for an XQuery 1.1 or a subsequent version of XQuery.

The XML Query WG is also chartered to continue its efforts to provide use cases and an interoperability test suite for XQuery.

Note that public working drafts will be made available at least once every three months. The minutes of each teleconference and face-to-face meetings will be archived.

Relationship with Other Activities

XML has become a strategic technology in W3C and in the global Web market.  The deliverable of the XML Query WG must satisfy the dependencies from the following Working Groups before it can advance to Proposed Recommendation.  Some dependencies to and from the following W3C Working Groups will require close cooperation during the development process; the requirements posed for the Query work by these WGs may change during the development process, which means the interdependency of the Query work with these WGs must be managed actively:

XSL WG and XML Linking WG

The XPath 1.0 language was jointly developed by the XSL and XML Linking WGs.  The XML Query WG will collaborate with the XSL WG to extend XPath 1.0 to an XPath 2.0 that covers the functionality that is common to both XML Query and XSL.

XML Schema WG

It is a goal of the XML Query work to be compatible with the work of the XML Schema Working group on XML Schema Part 2: Datatypes (XML Schema Part 2) and XML Schema Part 1: Structures (XML Schema Part 1).  For example, it should be possible to base query predicates on the existing DTD or XML Schema Part 1 definition of the content of an XML document and on the new data types being defined as part of the XML Schema Part 2. In addition the XML Query work will take advantage of the formal description of the contents of XML Schema defined in XML Schema: Formal Description (XML Schema: Formal Description).


The XML Query work will define a formal data model of XML documents. This model must be based on the model of the XML Infoset (XML Information Set). In case incompatibilities arise, requirements must be posed to the XML Core Working Group.  In any case, the final model used by the XML Query working group will have to be based on, and totally compatible with, the model of the XML Infoset.  In addition any XML Query definition of an XML fragment will take into consideration the XML Fragment Interchange specification (XML Fragment Interchange)


The XML Query work must take into account the iterators and filters component of the DOM, and wherever possible try to encompass those functionalities into the query language.  Alignment of the DOM and XQuery data models will also be investigated.

Internationalization WG

It is a goal of the XML Query work to ensure proper internationalization of the XML Query technology. The mission and scope of the Internationalization WG is to propose and coordinate any techniques, conventions, guidelines and activities within the W3C that help to make and keep the Web international. The XML Query WG and the Internationalization WG will work together to agree on specific I18N requirements and find solutions.

There are no requirements for co-development of features with the following WGs, but there are points of contact between their work and that of this WG, and thus logical dependency between their deliverables and those of this WG.  Requirements from these WGs are expected to be well suited for communication via documents:

WAI Protocols & Formats WG

Reuse of common constructs greatly facilitates accessibility; the WAI PF WG will review work on the XML query facilities to be sure cost/benefit design decisions are informed of the benefits of accessibility.


XML Query must strive for smooth interaction with the IETF DASL (DAV Searching & Locating) Working Group, in such a way that the XML query language can be easily incorporated into the DASL protocol.

Formal liaison between the XML Query Working Group and other W3C working groups, including the other XML working groups and the WAI (Web Accessibility Initiative) group, as well as organizations outside of the W3C, shall normally be accomplished by the exchange of documents (requirements, reviews, etc.) transmitted through the XML Coordination Group.

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

WG membership and decision process

The rules for the participation and decision process in the XML Query WG are regulated by the Common Procedures for XML Working Groups.  In addition, every participant must disclose all the IPR claims relevant to the XML Query working group according to the W3C's IPR Policy.

Participation in the XML Query WG is expected to consume at least half-day per week of each WG member's time, though the time commitment for the Chair and editors may require up to two full days per week.

The initial chair of this WG is Paul Cotton, Microsoft.


The XML Query WG (principals and alternates) shall communicate among its members using the WG mailing list w3c-xml-query-wg@w3.org) and with the members of other XML WGs through the w3c-xml-plenary@w3.org mailing list. The WG mailing list is archived; the archive is visible only to subscribers. A member-only list may also be used for non-technical purposes.

It shall communicate with the general public only through its Chair.


All documents appearing on the Member Web site must be respected by those authorized to consult the site as confidential within W3C. W3C Members must agree to use reasonable efforts to maintain this confidentiality and not to release this information to the general public or press.

excerpt from section 2.4.2 - Communication of the W3C Process

The proceedings of this working group are member-confidential, subject to exceptions made by the chair.

In particular, the XML Query WG mailing list archive and the Group home page are accessible by members only. (N.B. published documents may of course be discussed publicly.)

W3C, and all W3C Working Groups, are accountable to the Web community as a whole for the quality of W3C technical work. In support of this public accountability, this working group will periodically (e.g. monthly) make public a summary of all technical decisions made since the last public summary, and the rationales for these decisions.

Group Home Page

The XML Query WG has a home page that records the history of the group, provides access to the archives, meeting minutes, updated schedule of deliverables, membership list, and relevant documents and resources. It is maintained by the Chair in collaboration with the W3C staff contact.

Face-to-Face Meetings

Face-to-face meetings will be held as needed; it is expected that such meetings will be held about every two to three months.

Participation in face-to-face meetings is limited to principal members, formally approved alternates, and individual experts invited by the WG Chair. Invited experts who have not been formally approved as WG members have observer status and may not take part in decision-making.

W3C staff resource commitment

To be successful, we expect the XML Query WG to have approximately 20 to 25 active principal members for its duration.

The W3C will be represented by one principal and (optionally) one alternate WG member. The W3C staff resource commitment is no more than the minimum level of participation required of WG members in good standing by the W3C Process Document.

The W3C staff contact for this WG is Massimo Marchiori. The W3C Alternate Staff Contact is Liam Quin. It is expected that the total Team resources devoted to this WG will be about three fourths of a full-time engineer.

Communications resources for press and media relations and speaking appearances or meeting planning resources are amortized across the working groups in the XML Activity, and concentrated in the XML Coordination Group.