W3C Technical Architecture Group Status Report (August, 2009 - February, 2010)

This is a report from the W3C Technical Architecture Group to the W3C membership on TAG activities from August, 2009 through February, 2010.


In our previous status report we announced that the TAG had decided to focus primarily on three major areas of current interest:

  1. HTML
  2. Web Application Architecture
  3. Metadata Access and Formats

We have continued to use them as the organizing framework for the majority of our work: sections below discuss each of these, as well as TAG work in some other areas. We continue to put particular emphasis on working with the HTML WG to resolve issues relating to HTML5; we consider HTML5 to be a top priority for the success of the W3C and for the Web community in general, and we wish to support the HTML WG in their efforts to resolve issues promptly.


As the TAG has shifted its focus toward working closely with groups like the HTML WG, we have somewhat de-emphasized work on Recommendation-track documents and findings. In part for that reason, the TAG did not produce any formal working drafts or findings during the period covered by this report. We did, during the previous period, produce First Public Working Draft Usage Patterns For Client-Side URI parameters . The TAG may or may not decide to take this forward on the Recommendation track.

During the period covered by this report, several less formal drafts and planning documents were prepared and discussed, and these include:

In general, these have no official status except as part of the record of the TAG's discussions, but it is possible that we will in the future decide to evolve some of these into TAG Findings or Recommendations.


During the period covered by this report, the TAG held or participated in the following face-to-face meetings::

While at the November Technical Plenary, the TAG met in a joint session with the HTML working group.


HTML5 remains the single most important area of focus for the TAG. During the summer of 2009, the TAG read and reviewed the entire HTML5 draft specification. Based on that reading, we identified and prioritized issues at our September face-to-face meeting. The following subsections briefly summarize some of the more important issues we've worked on during this period:

Modularization of the HTML5 specification

As early as the 2008 Technical Plenary in Mandelieu, the TAG had identified to the HTML working group concerns about the modularity of the HTML5 specification, and also related concerns regarding its consistency with the the specifications for other standards (e.g. then-current use of the term "URL" in HTML5"). As a result of cooperative efforts among the HTML WG, the TAG, and other concerned parties, significant progress has been made on some of these issues. For example:

The TAG remains concerned that there may be other parts of the HTML5 specification that might better be published separately and/or that might benefit from tighter alignment with existing specifications.

HTML5 Language/Authoring Specification

Also raised at Mandelieu in 2008, and discussed in our previous status report was a concern that the then-current HTML5 drafts focused were more focused on user agent conformance than on clearly identifying the syntax, semantics, and other conformance requirements for HTML5 documents. The TAG therefore asked that the HTML5 WG consider the production of an HTML5 Language Reference document. Various forms for such a document were proposed by members of the HTML5 WG and by others. The HTML Working Group has proposed to address the TAG's concern, in part, by publishing a so-called "author's view" of the HTML5 specification. This is built from the same sources as the other versions of HTML5, but it is organized specifically to meet the needs of those who author HTML5 documents. The TAG has indicated general satisfaction with this direction, but there are some outstanding concerns regarding the degree of commitment by the HTML WG to setting clear goals for, ensuring the quality of, and maintaining over the long term this other version of the HTML5 specification.

The HTML WG has also published a First Public Working Draft of: HTML: The Markup Language.

HTML5 Decentralized Extensibility

The TAG has had a long-standing concern with the fact that HTML5, particularly in its text/html serialization, lacks robust facilities for decentralized extensibility of the language. This issue (which is tracked by the HTML WG as their ISSUE-41) remains unresolved.

During this period, the TAG took several steps to help address this issue, including:

Although not formally speaking on behalf of the TAG, TAG chair Noah Mendelsohn gave an invited plenary talk titled "Decentralized Extensibility in HTML5" (ppt, odp, pdf) at the November 2009 W3C TPAC.

Note that the HTML WG chairs have also put out a Call for proposals on Decentralized Extensibility, with a deadline of March 23rd. The TAG is currently preparing a response to that call.

HTML5 Microdata, Metadata, etc.

The TAG explored at length with the HTML WG group a number of concerns relating to data- and metadata-related facilities for use with HTML5. These included: did the inclusion of microdata facilities directly in HTML5 represent an inappropriate lack of modularity, and also an inappropriate lack of emphasis on RDFa, which is an existing W3C Recommendation? We also considered whether the namespace capabilities (or lack thereof) in HTML5's text/html serialization would unnecessarily complicate the use of RDFa.

As already noted, the removal of microdata to a separate specification represents some progress toward addressing the TAG's concerns. The HTML WG has also recently published HTML+RDFa: A mechanism for embedding RDF in HTML.

HTML5: Versioning and version indicators

At our joint meeting with the HTML5 WG at the 2009 TPAC, the TAG expressed some concern regarding the then-current treatment in the HTML working drafts of so-called "polyglot" documents, I.e. those that are HTML that is also well-formed XML, but which are served as Content-type text/html. As a result of these discussions, key text in the HTML5 draft was revised to eliminate ambiguities, and to make clearer that at least some such polyglot documents are indeed conformant. The TAG viewed this as a very positive result, and perhaps sufficient to completely resolve our concerns; as of now, the TAG is still discussing whether to advocate for yet more liberal support for polyglot documents, perhaps to include those that have explicit DOCTYPEs.

The TAG has also been debating the degree to which current HTML5 drafts would be suitable as a media type registration document, to replace the existing HTML 4-based registration. The most significant concern is the lack of explicit references to early specifications, such as to HTML 2 or to HTML 4.

HTML5 Other Issues

The TAG also participated with others in discussions of other HTML-related topics, including:

Web Application Architecture

The Web was initially a system for sharing documents, typically in HTML. Languages like Javascript were used occasionally to provide somewhat more dynamic rendering, or for aids to navigation. In recent years, a new class of Web applications has emerged. The browser is now used as a container for applications that may execute for extended periods, that integrate information from diverse sources, and that provide users with the ability to navigate among states while remaining in the same application. Some of these applications also store information for offline use. HTML is used not as a representation of an individual document, but as a framework for hosting complex program logic, which is typically coded in Javascript.

Not surprisingly, these new Web applications raise many architectural issues: What does the URI that "launched" the application identify, and how should URIs be used as the application presents new information to the user? How can security and privacy be maintained as these applications access and integrate information from multiple sources?

As discussed in our previous status report, the TAG decided in June 2009 to begin a more comprehensive exploration of the ways that Web architecture should evolve to support such Web Applications. An initial list of topics for exploration was assembled and discussed. During this period we continued our work in the following specific areas:

APIs and Privacy Policy

The TAG is working to understand and to assist in resolving concerns about the implementation of privacy policy for APIs such as geolocation. This topic has become controversial, in part because of differences of opinion between the W3C Geolocation working group and the IETF (GEOPRIV) effort. The W3C group issued a working draft that does not include explicit privacy controls; the IETF responded with a comment on that specification, requesting that GEOPRIV-like mechanisms be adopted, and offering assistance with the work.

The TAG held a number of meetings to discuss these concerns, which we understand will arise not just for geolocation, but for other APIs as well. In December of 2009, the TAG issued adopted a position that urges working groups working in these areas to include in their architectures the ability to communicate policy information so that it can be used to determine correct access to and retention of user data and resources. Addressing these concerns should be a requirement, although the details of how they are addressed may vary by application. Subsequently, Device Access and Policy Working Group chair Frederick Hirsch sent a note to the TAG citing a Geolocation WG resolution against including explicit policy rules, and inviting the TAG's assistance in further exploring the issue. Several notes and discussions have followed from that correspondence.


Privacy policy is just one API-related area of concern for the TAG; we expect to explore others in coming months.

Secrets in URIs

Several years ago, the TAG published its finding: The use of Metadata in URIs, which includes the Good Practice Note: URI assignment authorities SHOULD NOT put into URIs metadata that is to be kept confidential. Recently, Web-based systems have begun to emerge which do indeed rely on limiting distribution of URIs that contain either secret information in clear text, or tokens that must be kept confidential because they can grant access to sensitive information. That is, these systems distribute (often through email) URIs that give the recipient the capability of retrieving or modifying information that is intended to be kept secret from others. The TAG is actively considering the pros and cons of modifying its advice on putting confidential information into URIs.

URIs for Web Applications

As noted above, the TAG is considering options for further work on our First Public Working Draft Usage Patterns For Client-Side URI parameters .

Metadata access and representations

The TAG continues to explore several issues relating to publishing and accessing metadata on the Web.

Metadata Access

The TAG continues to review and discuss progress on the following IETF drafts:

The work described below on HTTP Semantics is in part supportive of the TAG's work on access to metadata.


The TAG is also interested in the formats and vocabularies that are used to encode and transmit metadata. As previously reported, at its June, 2009 face-to-face meeting, the TAG agreed to start work on a TAG Finding on this topic. We have had several discussions since, but actual drafting of a finding has not received much attention in recent months.

Other topics

In addition the primary focus areas discussed above, the TAG did work in several other areas:

HTTP Semantics

An informal interest group has been attempting to establish formal semantics for the HTTP protocol. Phone calls are held several times per month, and discussion is held on the public-awwsw@w3.org (archives). Although this is not a formal effort of the TAG, it was inspired in part by discussions held at the TAG. TAG member participates regularly, and the TAG discusses the progress of this work from time to time.

At the December TAG F2F, Jonathan Rees presented a formal approach that many TAG members felt was a very useful step toward developing a more rigorous specification of HTTP semantics.

Naming and URI Schemes

The TAG continued its explorations of URIs, URNs, URI schemes, and in particular the suitability of the http URI scheme in situations where flexible registration and naming semantics are required. We have also started to consider issues relating to the long term persistence of URI assignments. Henry Thompson and Jonathan Rees prepared revised draft Guidelines for Web-based naming.

URIs for use with Widget packaging

The TAG has several times considered the Widgets 1.0: Widget URIs. In general, the TAG believes that http-scheme URIs should be used to identify resources in most cases where such use is practical; the TAG is considering, in that context, the merits of having a separate widget scheme for use with widget packaging.

Content coding for Effecient XML Interchange

The TAG has expressed its gratitude to the EXI working group for their registration of content-coding tag EXI.

About the Technical Architecture Group

The Technical Architecture Group (TAG) was created in February 2001. Three TAG participants are appointed by the Director and five TAG participants are elected by the Advisory Committee. The mission of the TAG is stewardship of the Web architecture. Included in this mission is building consensus around principles of Web architecture, resolving issues involving Web architecture, and helping to coordinate cross-technology architecture developments inside and outside W3C.

Details on TAG activities can be found from the TAG home page. The TAG meets weekly via teleconference and several times each year in person. Summaries (such as this one) of the TAG's activity are provided periodically to the W3C Advisory Committee, W3C working group chairs, and to the public TAG mailing list (www-tag archive). The TAG welcomes public discussion of open issues, as well as proposals for new issues, on that same list. The TAG's previous report was published in July, 2009.

TAG Participants

The following changes in the membership have occurred since the last TAG report:

All new terms began on 1 February, 2010. Other continuing members of the TAG are:

No members have left the TAG during the period covered by this report. Dan Connolly is the W3C Staff Contact for the TAG.


Noah Mendelsohn, TAG co-chair

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