W3C Architecture Domain | XML

Charter of the Efficient XML Interchange Working Group

[This charter has been extended until 31 December 2008]

The Efficient XML Interchange Working Group is part of the W3C XML Activity and follows the Working Group process described in section 6.2 Working Groups and Interest Groups of the W3C Process Document. Except as specified in this charter, the Working Group follows the Common Procedures for XML Working Groups.

Table of Contents

  1. Mission
  2. Scope and Goals
  3. Out of scope
  4. Success criteria
  5. Deliverables and duration
  6. Expected milestones
  7. Coordination with Other Groups
  8. Working Group participation
  9. Meetings
  10. Communication
  11. Confidentiality
  12. Patent Policy


The main objective of the Efficient XML Interchange (EXI) Working Group is to develop a format that allows efficient interchange of the XML Information Set, based on the conclusions of the XML Binary Characterization Working Group.

Scope and Goals

XML has been enormously successful as a markup language for documents and data, but is not an optimal format for all purposes. The XML Binary Characterization Working Group established a set of use cases for which XML employment may be problematic. The Efficient XML Interchange Working Group is chartered to define an alternative encoding of the XML Information Set that addresses at least the minimum requirements identified by the XML Binary Characterization Working Group. The Working Group shall also consider properties that shouldn't be prevented, as listed in the second list of the decision tree. Such support will be considered as extensions to the XML Information Set or extensions introduced in the XML Schema 1.0 Post–Schema–Validation Infoset and in the XQuery 1.0 and XPath 2.0 data model.

The goals of this Working Group are:

  1. Fulfill the design goals of XML with the following exceptions:
    1. The interchange format must be compatible with the XML Information Set instead of being “compatible with SGML” (XML goal 3);
    2. For performance reasons, the format is not required to be “human–legible and reasonably clear” (XML goal 6);
    3. Terseness in efficient interchange is important (XML Goal 10).
  2. Address all requirements and use cases from the XML Binary Characterization Working Group;
  3. Maintaining the existing interoperability between XML applications, as well as XML specifications;
  4. Establish sufficient confidence in the proposed format, in particular establishing confidence that the performance gains are significant, and the potential for disruption to existing processors is small;

There are several approaches to achieve the integration with XML. The Working Group will provide at least one way for the new format to be both recognized as XML by existing parsers and also rejected in a meaningful way, such as by defining a new value for the pseudo–attribute encoding.

The Working Group will start by considering existing solutions and will evaluate each in terms of implementability and performance against the requirements and use cases documents produced by the XML Binary Characterization Working Group.

Out of scope

This Working Group is not chartered to:

  1. Introduce a new data model for XML;
  2. Develop an application specific format. Like XML itself, the new format must support a wide variety of applications.

Success criteria

Two of the entrance criteria used for the Last Call phase will be:

  1. the Working Group Note on the impact of the new format on existing XML technologies;
  2. the Working Group Note analyzing the performance gains of the new format, based on the criteria included in the measurement methodologies document. For example, in the case of compactness, the information compression is expected to be at most 20% larger than its equivalent ASN.1 PER, when a schema optimization is in use. Some of the analysis require to have an implementation and will be done during the Candidate Recommendation phase, such as processing efficiency.

Careful review will be given to the feedback from other Groups, within and outside the XML Activity. Findings that suggest that the proposed format has a significant impact and disruption of existing XML technologies and processors might dissuade W3C from advancing the format to W3C Candidate Recommendation, or might persuade W3C to do so but without referring to the format as a flavor of XML.

Two of the entrance criteria used for the Proposed Recommendation phase will be:

  1. demonstrate the performance gains of the new format, based on the prior analysis done as an entrance criteria of the Last Call phase. In addition, an analysis regarding the properties that need an implementation to be evaluated, such as processing efficiency, will be conducted.
  2. demonstrate at least two interoperable implementations supporting all the features provided in the specification. One of the implementations must be available for public use.

The Working Group may at any stage recommend the use of an already published format, provided that it satisfies the above criteria, instead of providing a W3C Recommendation.

Deliverables and duration


The Working Group is expected to produce:


The expiration date of this charter is 31 December 2007.

Expected milestones

The following milestones are proposed. As usual, the duration of the review period must be negotiated with other groups, in particular the XML Coordination Group for the Last Call phase duration.

December 2005
Working Group created
February 2006
First face–to–face meeting.
May 2006
First draft of the Working Group Note providing the analysis of the performance measurements and of the Test Suite
September 2006
First Public Working Draft of the efficient XML interchange format.
January 2007
Last Call Working Draft, along with the analysis of its impact on existing XML applications and specifications, and the analysis of the performance gains.
June 2007
Candidate Recommendation.
October 2007
Proposed Recommendation, along with the final analysis of the performance gains, based on implementation reports.

Coordination with Other Groups

W3C Groups

The Working Group should coordinate its efforts with W3C Working Groups, in particular in the XML Activity as well as the Technical Architecture Group.

External Groups

MPEG-7 has an ISO standard binary infoset serialization, BiM, and is currently working on a second version.
MPEG-4 is currently re–evaluating its BIFS encoding, and may be interested in providing input notably regarding efficient decoding on small devices.
Fast Infoset (ITU-T Rec. X.891 (2005) | ISO/IEC 24824-1) is in the process of being approved within the ISO.
Web3D has explicitly asked the W3C about binary formats, and has researched them itself.

Working Group participation

Effective participation is expected to consume one workday per week for each Working Group participant; two days per week for editors. The Chair shall ensure that the criteria for Good Standing are understood and followed.

To be successful, we expect the Working Group to have 10 or more active participants for its duration.


The initial chairs of this Working Group are Oliver Goldman, Adobe Systems, and Robin Berjon, Expway.

W3C Team resources

The initial W3C Team contact is Carine Bournez. It is expected that this Working Group will consume about 0.5 FTE, including administrative logistics.


The Working Group will have distributed meetings, one to two hours every week, and face–to–face meetings, every two to three months.


The Working Group will utilize a W3C Member mailing list, member-exi-wg@w3.org.


The proceedings of this Working Group are “Member-only”, subject to exceptions made by the Chair, after consultation with the Working Group.

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.

Philippe Le Hégaret, Architecture Domain Leader, following comments from many individuals
Last modified $ Date: 2005/09/29 19:06:49 $