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This is the public web page for the Efficient XML Interchange (EXI) Working Group of the World Wide Web Consortium (W3C). The EXI group is part of W3C's XML Activity. Here we present literature and data that may be of interest to the public. There is also a private page for members of the EXI group, for internal information.
The objective of the Efficient XML Interchange Working Group is to develop a specification for an encoding format that allows efficient interchange of the XML Information Set, and to illustrate effective processor implementations of that encoding. This work is based on the conclusions of the XML Binary Characterization Working Group.
The group's original charter covered the period December 2005 until 31 December 2007. It has been extended until 31 December 2008.
Selected publications in the order of most recent first:
The Charter of the Efficient XML Interchange Working Group defines the deliverables expected of the group.
In order to promote interoperability between implementations and to validate the clarity of the EXI specification, a number of EXI encoded documents have been made available for example purposes. Those interested can compare their own EXI encodings to these examples and discuss their questions/comments on the public-exi@w3.org (Archives). The U.S. Naval Postgraduate School generated the examples (on behalf of the Web3D Consortium) using AgileDelta's implementation of the third draft of the EXI format specification, but has not been tested by the EXI working group. Although these examples are not normative, they should prove useful in developing EXI implementations and in focusing discussion to improve the EXI format specification.
The EXI framework is now available for download! This testing framework was created for the purpose of obtaining empirical data about format properties. In this release, the framework can be used to measure Processing Efficiency and Compactness over a wide variety of XML documents collected by the WG. The framework includes support for in-memory and network testing, the latter is particularly useful to measure the performance of a format relative to the available bandwidth. See the Release Notes for further information.
(As of July 2008).
In mid November 2006, the EXI group completed measurements of various candidate encodings and processors for an efficient XML interchange. Based on the results of that work the group has selected Efficient XML to be the basis for the proposed encoding specification. Present work centers around integrating some features from the other measured format technologies into Efficient XML, particularly variations for both more efficient structural and value encodings. Additionally, we are drafting the specification of this format, making some further measurements of the format in a small variety of network exchanges, and preparing a final release of the full measurements data and accompanying analysis.
The First Public Working Draft of the EXI specification was originally expected in February 2007 (immediately after the W3C multi-group meeting, at which we consulted with other Working Groups). This has been delayed while we have integrated features for efficient structural and value encodings, schema mapping, support for specialized codecs, and compression. The First Public Working Draft of the Efficient XML Interchange Format 1.0 has been published on July 16th, 2007.
The two previously separate documents, the Measurements Note (Working Draft), and the Analysis Note (publicly available), have been republished as a single Working Draft on July 25th. Additionally, all of the raw measurement data are available.
In December 2007, two additional documents have been published: a Primer and a Best Practices document, as long as a second Working Draft of the format specification. It includes the specification of the schema-informed mode and a number of fixes.
In March 2008, a 3rd Working Draft of the format specification has been published (see also: list of changes from the previous draft).
In July 2008, a 4th and complete Working Draft of the format specification is available for review. A draft note on the Evaluation of the EXI Format with reference to the Properties identified by the XBC Working Group, relative to XML, gzipped XML and ASN.1 PER, is published. The Working Group plans to enter Last Call for comments during the summer.
The Efficient XML Interchange Working Group was chartered to define an alternative encoding of the XML Information Set, that addressed the requirements identified by the XML Binary Characterization Working Group, while maintaining the existing interoperability between XML applications and XML specifications.
The XML Binary Characterization Working Group conducted work between March 2004 to March 2005, to gather information about uses cases where the overhead of generating, parsing, transmitting, storing, or accessing XML-based data, might be deemed too great within the context of those use cases. XBC also characterized the properties that XML provides as well as those that are required by the use cases, and established measurements to help judge whether XML 1.x and alternate encodings provided the required properties. In that group's Characterization document, the XBC Working Group recommended future work.
The task of this Working Group is to jointly establish and optimize, the performance of an alternate, binary, encoding of XML. At the same time, disruption to existing processors, and impact on the complex real-world uses of XML, must be minimized. The Working Group started by considering existing solutions and has evaluated each in terms of implementability and performance against the requirements produced by the XBC Working Group. We gathered together a test data set of more than 10000 documents in 30 or so XML vocabularies, from a broad range of use case groups, such as Scientific, Financial, Electronic (those intended for human consumption), Storage (intended as data stores), etc. The existing solutions, and candidate base technologies for a potential EXI format, were then measured over a number of merit criteria, within a benchmark framework based on japex. The first draft of the measurements were presented in July 2006, in the Efficient XML Interchange Measurements Note and Analysis of the EXI Measurements reports.
The Efficient XML Interchange Working Group operates according to this charter. You can get involved by joining the W3C.
The list of the Working Group's participants is available on the WG status page.
The public mailing list for technical discussion with the Working Group is public-exi@w3.org (Archives).
We plan to reach the Last Call working draft stage mid-2008 and target Candidate Recommendation in December 2008.
W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent.
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