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Last modified: February 24, 2000
W3C XML Working Groups

The Extensible Markup Language (XML) designed for 'structured document interchange on the Web' is formally a part of the W3C Architecture Domain. "Although originally envisaged to meet the challenges involved in large-scale publishing, XML is set to play an increasingly important role in the markup of a wide variety of data on the Web" [1999-02-23]. The XML Activity Lead is Dan Connolly. As of late 1998, several W3C Groups had been organized to manage and conduct the XML design and development work.

The following overview of the XML Working Groups and their published deliverables is taken substantially from the official W3C XML Activity Statement -- a document which should be consulted in all cases as the authoritative, current statement. A schedule of XML events is provided in the W3C's main XML document.

XML Activity, Third Phase

[September 14, 1999] Update on the XML Activity, Third Phase. From the XML Activity document. "The first phase of the XML Activity, started in June 1996, culminated in the W3C XML 1.0 Recommendation, issued February 1998. In the second phase, work proceeded in a number of working groups in parallel, resulting in the January 1999 Recommendation Namespaces in XML and the June 1999 Recommendation for Style Sheet linking. In September 1999, we begin the third phase, continuing the unfinished work from the second phase and introducing a Working Group on XML Query and plans for a Working Group on XML Packaging." In addition to the XML Coordination Group, XML Working Groups in this third phase include: (1) XML Query Working Group, (2) XML Schema Working Group, (3) XML Linking Working Group, and the (4) XML Core Working Group. See also the announcement from Jon Bosak (Sun Microsystems, XML Coordination Group Chair).

XML Coordination Group

WG Chair

"The chair of the XML Coordination Group is Jon Bosak of Sun Microsystems."

WG Description

The membership of the XML Coordination Group is "the chairs of the individual Working Groups. Its role is to provide a forum for coordination between the Working Groups of the XML Activity, and between the XML Activity and other parts of W3C, and between the XML Activity and other organizations. In particular, the co-ordination group:

  • Coordinates workflow
  • Watches out for dependencies between Working Groups
  • Creates and dissolves WGs within its chartered scope (rare but essential)
  • Sets master WG/IG/CG meeting schedule
  • Maintains the public roadmap (the document you are now reading)
  • Notifies IG of changes they should be aware of
  • Manages crises
    • Turns hard policy/architecture questions over to the Interest Group
    • Deals with upper W3C echelons when necessary
    • Deals with aggrieved member organizations when necessary
  • Maintains liaison inside and outside the W3C
  • In particular, gathers and forwards requests for additional requirements to the appropriate WG(s)
  • Forwards requests for process changes originating in the IG upward into the larger W3C
  • Suggests/proposes items relating to policy and architecture to the IG for its consideration"

Other References

XML Query Working Group

WG Chair

Paul Cotton of IBM is the chair of the XML Query Working Group. W3C contact: Massimo Marchiori.

XML Query Working Group Description

"Following the W3C Query Languages Workshop (QL'98), 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. The XML Query Working Group plans to develop requirements in 1999 and continue with design work in 2000."

See the separate document on "XML and Query Languages" with references.

XML Schema Working Group

WG Chairs

The co-chairs of the XML Schema Working Group are Dave Hollander of CommerceNet and C. M. Sperberg-McQueen, of the University of Illinois at Chicago and the W3C.

WG Published Deliverables

XML Schema Requirements

  • "XML Schema Requirements." W3C Note 15 February 1999. Edited by Ashok Malhotra (IBM) and Murray Maloney (Veo Systems Inc.). The document 'specifies the purpose, basic usage scenarios, design principles, and base requirements for an XML schema language.[local archive copy]

XML Schema Definition Language - Third Working Draft

See: XML Schema Definition Language - Third Working Draft, 1999-11-05.

XML Schema Definition Language - Second Working Draft

  • XML Schema Part 1: Structures. Reference: W3C Working Draft 24-September-1999, edited by Henry S. Thompson (University of Edinburgh), David Beech (Oracle), Murray Maloney (Commerce One), and Noah Mendelsohn (Lotus). Part 1 "proposes facilities for describing the structure and constraining the contents of XML 1.0 documents. The schema language, which is itself represented in XML 1.0, provides a superset of the capabilities found in XML 1.0 document type definitions (DTDs). . . The purpose of the Structures specification is to provide an inventory of XML markup constructs with which to write schemas." Such a schema is used "to define and describe a class of XML documents by using these constructs to constrain and document the meaning, usage and relationships of their constituent parts: datatypes, elements and their content, attributes and their values, entities and their contents and notations. Schema constructs may also provide for the specification of additional information such as default values. Schemas are intended to document their own meaning, usage, and function through a common documentation vocabulary. Thus, the Structures specification can be used to define, describe and catalogue XML vocabularies for classes of XML documents. Any application that consumes well-formed XML can use the XML Schema: Structures formalism to express syntactic, structural and value constraints applicable to its document instances. The Structures formalism will allow a useful level of constraint checking to be described and validated for a wide spectrum of XML applications. However, the language defined by this specification does not attempt to provide all the facilities that might be needed by any application. Some applications may require constraint capabilities not expressible in this language, and so may need to perform their own additional validations."

  • XML Schema Part 2: Datatypes. Reference: W3C Working Draft 24-September-1999, edited by Paul V. Biron (Kaiser Permanente, for Health Level Seven) and Ashok Malhotra (IBM). The Datatypes document "specifies a language for defining datatypes to be used in XML Schemas and possibly elsewhere." As explained in the W3C's XML Schema Requirements document, the Datatypes design is motivated by the recognition that "document authors, including authors of traditional documents and those transporting data in XML, often require a high degree of type checking to ensure robustness in document understanding and data interchange." In many cases, "validity constraints exist on the content of the [XML] instances that are not expressible in XML DTDs. The limited datatyping facilities in XML have prevented validating XML processors from supplying the rigorous type checking required in these situations. The result has been that individual applications writers have had to implement type checking in an ad hoc manner. This [Datatypes] specification addresses the need of both document authors and applications writers for a robust, extensible datatype system for XML which could be incorporated into XML processors." The facilities in the Datatypes WD have been designed in light of the formal requirements, which stipulate that the XML Schema Language must: (1) provide for primitive data typing, including byte, date, integer, sequence, SQL & Java primitive data types, etc.; (2) define a type system that is adequate for import/export from database systems (e.g., relational, object, OLAP); (3) distinguish requirements relating to lexical data representation vs. those governing an underlying information set; and (4) allow creation of user-defined datatypes, such as datatypes that are derived from existing datatypes and which may constrain certain of its properties (e.g., range, precision, length, format)."

XML Schema Definition Language - First Working Draft

Expected WG Deliverables

"The Schema Working group plans to deliver Requirements, Working Drafts, and Proposed Recommendations on data typing and schema language in 1999."

WG Description

"While XML 1.0 supplies a mechanism, the Document Type Definition (DTD) for declaring constraints on the use of markup, automated processing of XML documents requires more rigorous and comprehensive facilities in this area. Requirements are for constraints on how the component parts of an application fit together, the document structure, attributes, data-typing, and so on. The XML Schema Working Group is addressing means for defining the structure, content and semantics of XML documents.

"The Working Group is considering several submitted proposals:

  • XML-Data. W3C Note 05-Jan-1998. "This paper describes an XML vocabulary for schemas, that is, for defining and documenting object classes. It can be used for classes which as strictly syntactic (for example, XML) or those which indicate concepts and relations among concepts (as used in relational databases, KR graphs and RDF). The former are called 'syntactic schemas;' the latter 'conceptual schemas'."

  • XML-Data Reduced. Draft Version 3-July-1998, version 0.21. By Charles Frankston (Microsoft) and Henry S. Thompson (University of Edinburgh). "The XML-Data submission contained many new ideas that an XML schema language could support. This document refines and subsets those ideas down to a more manageable size in order to allow faster progress toward adopting a new schema language for XML. Some of the inconsistencies in the XML-Data submission are cleaned up, and some changes have been made based on comments received since the XML-Data submission was posted. This note is a refinement of the January 1998 XML-Data submission" [local archive copy]

  • "[Microsoft] XML Schema Developer's Guide" Andrew Layman [XML-DEV 18-May-1999]: "'XML-Data Reduced' (XDR) refers to a trimmed and improved version of the XML-Data schema syntax. The original XML-Data submission can be found at Information on XML-Data Reduced is at'." Note: 'XDR' in this context not to be confused with XDR: External Data Representation Standard (Network Working Group, Request for Comments: 1832, August 1995).

  • DCD. NOTE-dcd-19980731, Submission to the World Wide Web Consortium 31-July-1998. "This document proposes a structural schema facility, Document Content Description (DCD), for specifying rules covering the structure and content of XML documents. The DCD proposal incorporates a subset of the XML-Data Submission and expresses it in a way which is consistent with the ongoing W3C RDF (Resource Description Framework) effort; in particular, DCD is an RDF vocabulary. DCD is intended to define document constraints in an XML syntax; these constraints may be used in the same fashion as traditional XML DTDs. DCD also provides additional properties, such as basic datatypes."

  • SOX. Schema for Object-oriented XML. NOTE-SOX-19980930, Submitted to W3C 19980915. "This document proposes a schema facility, Schema for Object-oriented XML (SOX), for defining the structure, content and semantics of XML documents to enable XML validation and higher levels of automated content checking. The SOX proposal is informed by the XML 1.0 [XML] specification as well as the XML-Data submission (XML-Data), the Document Content Description submission (DCD) and the EXPRESS language reference manual (ISO-10303-11). SOX provides an alternative to XML DTDs for modeling markup relationships to enable more efficient software development processes for distributed applications."

  • DDML. Document Definition Markup Language (DDML) Specification, Version 1.0. NOTE-ddml-19990119, W3C Note, 19-Jan-1999. "This document proposes Document Definition Markup Language (DDML), a schema language for XML documents. DDML [previously 'XSchema'] encodes the logical (as opposed to physical) content of DTDs in an XML document. This allows schema information to be explored and used with widely available XML tools. DDML is deliberately simple, providing an initial base for implementations. While introducing as few complicating factors as possible, DDML has been designed with future extensions, such as data typing and schema reuse, in mind."

Other References

XML Linking Working Group

WG Chair

"The chair of the Linking WG is Bill Smith, of Sun Microsystems." A co-chair, Tim Bray, was appointed (?) in July/August 1999 (see below on XLink). Ron Daniel of Datafusion serves as the XML Linking Interest Group chair. W3C staff contact: Daniel Veillard

WG Published Deliverables

  • [July 09, 1999] XPath: XML Path Language (XPath) Version 1.0. W3C Working Draft 9-July-1999. Edited by James Clark and Steve DeRose (Inso Corp. and Brown University). "XPath is a language for addressing parts of an XML document, designed to be used by both XSLT and XPointer." Available also in XML format.
  • [July 09, 1999] XML Pointer Language (XPointer). W3C Working Draft 9-July-1999. Edited by Steve DeRose (Inso Corp. and Brown University) and Ron Daniel Jr. (DATAFUSION, Inc.). "This document specifies a language that builds upon the XML Path Language (XPath), to support addressing into the internal structures of XML documents. In particular, it provides for specific reference to elements, character strings, selections, and other parts of XML documents, whether or not they bear an explicit ID attribute, using traversals of a document's structure and choice of parts based on their properties such as element types, attribute values, character content, and relative position, containment, and order."
  • XML XLink Requirements Version 1.0. Edited by Steven J. DeRose. W3C Note 24-Feb-1999. [local archive copy]
  • [August 04, 1999] XLink to be advanced: Tim Bray, writing as "Co-Chair, W3C Xlink Working Group," posted a note to the XML-DEV list on August 04, 1999 to this effect: "And I don't think it's out of place to report in this venue that the XLink WG has placed itself on a very short deadline to get its long-overdue job done. Watch for a rapid succession of Working Drafts converging to a Proposed Recommendation in the immediate future."
  • XML XPointer Requirements Version 1.0. Edited by Steven J. DeRose. W3C Note 24-Feb-1999. [local archive copy]
  • XPointer-Information Set Liaison Statement. Edited by Steven J. DeRose. W3C Note 24-Feb-1999. [local archive copy]
  • [XML Linking Language (XLink) World Wide Web Consortium Working Draft 3-March-1998, WD-xlink-19980303.]
  • [XML Pointer Language (XPointer) - World Wide Web Consortium Working Draft 03-March-1998, WD-xptr-19980303.]

Expected WG Deliverables


WG Description

"The XML Linking Working Group is designing hypertext links for XML. Engineers defining the way that links are to be written in XML have made a distinction for links between objects - 'external' links, and 'internal' links to locations within XML documents, and both types will receive detailed treatment by this group. The objective of the XML Linking Working Group is to design advanced, scalable, and maintainable hyperlinking and addressing functionality for XML."

"The working drafts XML Linking Language (XLink) and XML Pointer Language (XPointer) represent the basis on which the work of the Linking WG will proceed."

Other References

XML Core Working Group

WG Chairs

Paul Grosso of Arbortext and David Megginson of Megginson Technologies are co-chairs of the working group. W3C contact: Dan Connolly.

XML Core Working Group Description

[September 14, 1999] "The mission of the XML Core Working Group is to elaborate the XML 1.0 Recommendation, maintaining it in response to reported errata and other comments, and providing essential supplementary materials. This working group continues the work of the XML Syntax, XML Fragment, and XML Information Set Working Groups, and provides a forum for continued work on XML Namespaces. Working Drafts on XML Fragment Interchange, XML Information Set, and Canonical XML are available for review. The XML Core Working Group plans to deliver a Proposed Recommendations for Canonicalizing XML, Fragment Interchange, and the Information Set during the Fall of 1999.

XML Information Set Working Group [Phase 2]

WG Chair

"The chair of the Information Set WG is David Megginson, invited expert."

WG Published Deliverables

Expected WG Deliverables

"The Information Set Working Group plans to have completed the First public XML Information Set Working Draft to be released by the end of 1998 and a Proposed Recommendation by Spring 1999."

WG Description

"The XML 1.0 Recommendation describes the physical representation of XML documents: the use of brackets, character strings and other 'nuts and bolts' which make up the language. The Information Set Working Group is looking at more abstract descriptions of XML documents in terms of document tree structures, elements, their attribute lists and so on. The idea is to provide a common reference set that other specifications can use and extend to construct their underlying data models, thus helping to ensure interoperability among the various XML-based specifications and among XML software tools in general."

Other References

XML Fragment Working Group [Phase 2]

WG Chair

The chair of the XML Fragment WG is Paul Grosso of ArborText.

WG Published Deliverables

  • [July 01, 1999] The W3C's XML Fragment Working Group has published a new working draft of the document XML Fragment Interchange (W3C Working Draft 1999-June-30), edited by Paul Grosso (Arbortext) and Daniel Veillard (W3C). Abstract: "The XML standard supports logical documents composed of possibly several entities. It may be desirable to view or edit one or more of the entities or parts of entities while having no interest, need, or ability to view or edit the entire document. The problem, then, is how to provide to a recipient of such a fragment the appropriate information about the context that fragment had in the larger document that is not available to the recipient. The XML Fragment WG is chartered with defining a way to send fragments of an XML document -- regardless of whether the fragments are predetermined entities or not -- without having to send all of the containing document up to the part in question. This document defines Version 1.0 of the [eventual] W3C Recommendation that addresses this issue." The working group "considers its charter discharged" with the publication of this new WD: "the draft is technically ready to go to Proposed Recommendation, but the WG decided to hold at this stage to await some implementation experience and to allow possibly related work in other WGs to progress further before submitting this draft for PR." Available also in XML format, [local copy]

  • XML Fragment Interchange - W3C Working Draft 12-APR-1999. Edited by Paul Grosso and Daniel Veillard. [local archive copy]

  • [April 13, 1999] Announcement for XML Fragment Interchange WD 19990412.

  • "XML Fragment Interchange" specification. W3C Working Draft 03-MAR-1999. Edited by Paul Grosso and Daniel Veillard. Available online in both HTML and XML format. Local archive copies: HTML, XML

  • XML Fragment Interchange Requirements Version 1.0. W3C Note 23-Nov-1998, NOTE-XML-FRAG-REQ-19981123. Edited by Paul Grosso (Arbortext).

Expected WG Deliverables

"The Fragment Working Group expects to issue a W3C Proposed Recommendation for Fragment Interchange by Summer 1999."

WG Description

The XML standard supports logical documents composed of possibly several entities. It may be desirable to view, edit, or interchange one or more of the entities or parts of entities without interchanging the entire document. The problem, then, is how to provide to a recipient of such a fragment the appropriate information about the context that fragment had in the larger document.

"The goal of the Fragment Working Group is to define a way to send fragments of an XML document without having to send all or part of the parent document as well. The delivered fragments can either be viewed or edited immediately or accumulated for later use, assembly, or other processing.

Other References

XML Syntax Working Group [Phase 2]

WG Chairs

"The co-chairs of the XML Syntax WG are Tim Bray, invited expert, and Joel Nava of Adobe."

WG Published Deliverables

Expected WG Deliverables

"The Syntax Group plans to deliver:

  • Proposed Recommendation for the XML Style Sheet Linking Version 2
  • Proposed Recommendation for the XML profile
  • Proposed Recommendation for Canonicalizing XML
all during the middle of next year (1999)."

WG Description

"The XML Syntax Working Group is concerned with several aspects of XML:

  • XML Style Sheet Linking. Since XML has no pre-defined set of tags like HTML's P and H1, information about how to display elements must be given in a stylesheet. This is a bit more work, but it provides tremendous flexibility and facilitates managing consistency across large sets of documents. For details, see the W3C Style Sheets Activity and the CSS and XSL home pages.
  • Defining an XML profile, consisting of a simplified and reduced set of XML features which might specify, for example, a sub-set of the full recommendation that a given device might support, or a given XML application might use.
  • Canonicalizing XML which involves finding a single or "canonical" version of every possible possible form of the same document (by reducing white space, mapping quote marks to a standard form, etc.) with a view to using that standard form for the purpose of applying digital signature technology. An algorithm is applied to the canonical form of the document to generate a large number. If the document is tampered with in any way when it is sent down the wire, the algorithm applied to the document will generate a different number from the original, showing up even minute changes to have taken place.
  • Tracking Internationalization Developments. One part of this work, for example, concerns the use by XML, of Universal Character Set defined by ISO/IEC 10646 and Unicode. The goal is to arrange that each time these standards are extended, that the XML specification is automatically updated accordingly.
  • Errata to XML 1.0. The group plan to track errata in the XML Recommendation."

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