Category: Meeting summaries

Thursday, June 4th 2009

Permalink 06:14:00 pm, Categories: Meeting summaries

POWDER is a Proposed Recommendation

The headline says it all!

See the announcement from W3C.

The W3C membership now has a chance to review the docs and approve (or not) the final transition to Recommendation. As far as the working group is concerned, the specification is complete. Work will continue, of course, on deployment and the development of new applications and community building. Although the specs are done, the work never stops...

Phil ARCHER

Monday, April 6th 2009

Permalink 09:54:52 am, Categories: Meeting summaries

The What and Why of the Third Last Call

Since making our second Last Call for comments at the end of last year we've responded to all of them and have been completing work on the tools - the processors, the XSLTs and so on - all of which has now been done.

So why aren't we at PR yet? There are a couple of reasons for this. There has been an ongoing battle between (WG member) Stasinos Konstantopoulos and (W3C team member) Eric Prud'hommeaux over whether the POWDER Semantic extension applies to the data layer or the application layer. The two protagonists have agreed to differ whilst the document has gone forward.

The second issue that has arisen concerns the other area that has prompted a lot of comment - the canonicalisation section of the grouping doc. Despite many changes over the last year or so and input from the Internationalisation WG, (W3C team member) Thomas Roessler spotted more problems with this section.

After a lot of e-mail bouncing around on, I'm sorry to say, a team-only list, I had a long conversation with Thomas and (Semantic Web lead) Ivan Herman. Some context:

The Semantic Web (RDF, OWL, SPARQL etc.) is written solely about URIs, not IRIs. Furthermore, all URIs are opaque strings - they have no meaning. This goes back to Jeremy Carroll's useful distinction between "http://www.example.com" and <http://www.example.com>. In other words, for RDF etc. our issue of processing URIs/IRIs as meaningful strings doesn't arise.

IRIs - that is, URIs written in things like Cyrillic script, Japanese Kanji etc. - are going to be more important in the coming 12 - 18 months (according to Thomas who, among other things, represents W3C at ICANN and so has a good grasp of such things). For POWDER not to be useful now and in the near future across all parts of the Web would limit its potential usefulness.

As we have discovered, the encoding of IRIs and International Domain Names is less than clear. However, there is a recognised path to take in this area which involves converting IRIs into ASCII - essentially converting IRIs to URIs.

It is not the POWDER WG's job or wish to solve the whole issue, neither is it within our ability to do so.

The POWDER to POWDER-BASE transform XSLT doesn't do any of the canonicalisation stuff, and it would be hard, if not impossible for it to do so. Therefore, strictly speaking, some form of pre-processing is already necessary before the XSLT is applied (the Perl script does do the canonicalisation but now needs a bit of work).

Given all of the above, the group was faced with a choice between either making significant edits in all its documents to talk only about URIs or, as we have done, further amending the canonicalisation section to introduce the ToASCII function as defined in RFC 3490. It is this change that has prompted the new Last Call announcement, open until Monday 27 April. The documents published on 3 April to coincide with the Last Call reflect all the changes made following comments received in the previous calls and, with the exception of the highlighted sections of the Grouping of Resources document on canonicalisation, are considered stable.

One important, although editorial, change worth highlighting is in the Description Resources document. The definition of the describedby relationship type and the two POWDER Content Types is much improved. describedby is now included in the IANA registry of ATOM Link relationship types.

The Test Suite has been significantly updated in the 3 April version and is now unlikely to change significantly (we may add some new tests for the canonicalisation section). Perhaps rather perversely, the test suite does include a test for the informative section on HTTP Link. The Primer is considered stable and very unlikely to change further.

Minor adjustments to the POWDER Processors are in progress and, notwithstanding changes prompted by the last call, the group is expecting to go to Proposed Recommendation in May.

Phil ARCHER

Friday, January 16th 2009

Permalink 02:21:41 pm, Categories: Meeting summaries

Situation Report 16 January 2009

The group's charter expired at the end of December so we're in something of a state of limbo (one might say unchartered territory). However, a lot of work is being done to get us ready for a request for transition to PR. The links below are all very much temporary but they are all up to date and reflect the true status of the group's work (the homepage and published documents are not being updated at the moment). Several tools are done and dusted:
  • The Validator. This is expected to move to validator.w3.org in due course
  • Perl-based processor. Again, this should move to a new home soon. There are minor improvements to make but it implements POWDER.
  • Semantic Processor. This is not a complete application, nor is it a conformant POWDER Processor, but is a command line-driven exemplar of POWDER-S. It uses Jena and Pellet to return descriptions of a given URI based on a given POWDER-S document.
Tools have also been produced that implement the transformations defined in the Formal document. An implementation report is being maintained. The POWDER XML Schema is also being debugged. Again, it's almost there. Actually, there are several interlinked schemata to handle POWDER and POWDER-BASE. The GRDDL transformation links will be included when we next make these available. A second, more sophisticated POWDER processor is close to completion. Based on PHP, it uses the schema to validate POWDER documents (the Perl-based processor uses the same code as the validator). Finally, most of the documents have been updated. It would be improper to link to them here but if you want to see updated versions of the DR, Grouping and Formal docs, plus the Primer and Test Suite, please get in touch and I'll send you the URIs. We're nearly there. Thankfully.
Phil ARCHER
Permalink 01:56:05 pm, Categories: Meeting summaries

Resolution of Open Questions from the Web Content Label XG in POWDER

The POWDER WG was formed following the Web Content Label Incubator Activity (WCL-XG). In its final report, the XG noted a total of 17 Open Questions, all of which have been resolved by POWDER. Note that cLabel was the term used in the XG: the equivalent term in POWDER is Description Resource (DR)

OQ 1:It is an open question whether there may be a requirement for some forms of cLabel that involve editing those resources.
The use cases presented do not call for DRs to be embedded within the content they describe. On the contrary, the expected use of POWDER strongly suggests that DRs should always be separate.
OQ 2:Should WCL-XG be successful in securing a WG charter, the abstract model for resource grouping will itself come under full scrutiny with a view to its publication either as a WG Note or a full Recommendation in its own right.
The abstract model developed in the XG is the basis for POWDER: Description Resources (a recommendation track document).
OQ 3:The mechanism for exposing properties of resources should by preference be both standard and be cLabel based. However, the precise workings of this have not been examined and are for further study.
The mechanism is fully developed in POWDER.
OQ 4:If successful in securing a WG charter, the group will need to address how to resolve situations in which scoping statements do not match.
The WG has taken the view that it is not practical to make it impossible for DR authors to create scope statements - now called IRI sets - that do not conflict. The Outline Methodology section of the Grouping document together with the short section on the safe use of regular expressions make it clear that mistakes are possible. A simple to use tool has been created to allow DR authors to develop and test their IRI set definitions.
OQ 5:It is an open question as to whether access to label repositories should be governed by a standard protocol.
OQ 6:It is also an open question as to whether a repository should provide a bulk data transfer capability alongside whatever capabilities it offers for transfer of description, cLabels and packages.
Open Questions 5 and 6 are covered by Section 4.4 of the Description Resources document.
OQ 7: HTTP Link Header
The group has been active in promoting the reinstatement of the HTTP Link Header and in the discussion surrounding the registration of relationship types. The relevant Internet Draft is very likely to reach RFC status during the first half of 2009 - shortly after the anticipated time when POWDER will become a Recommendation. The WG therefore has retained discussion of HTTP Link in its documentation but has flagged the relevant section as informative.
OQ 8:The form of authentication and certification mechanisms for cLabels requires further study.
This remains true - however, such a study is to be carried out by the individual labelling authority such that an appropriate mechanism for the particular application is implemented rather than demanding a single 'one size fits all' approach. POWDER provides a number of features designed to allow various authentication methods.
OQ 9: There is also work to be done to more clearly define the roles of various players in the trust chain, such as labeling authority, certification provider etc.
Section 5 of the Description Resources document discusses several different trust models that might be applied to POWDER.
OQ 10:It is not clear how labels on transcluded elements relate to any labels on the content that initiates the transclusion.
The word 'transclusion' was misused here, however, it is the nature of HTTP and RDF that each description of a resource is made and processed separately. Therefore, elements within an HTML page may well have different descriptions from the page itself. DR authors should be aware of this.
OQ 11:It is not clear whether it is useful or necessary to identify individual portions of content and to assign them individual labels, or to be able to provide labels that refer only to the resource without any transclusion.
It was resolved that fragment identifiers would not be part of the grouping mechanism. However, they may be supported in the extension mechanism as discussed in Section 2.1 of the Grouping document.
OQ 12:It is also not clear how redirection of HTTP requests affect the interpretation of a cLabel that refers to the non-redirected URI but does not refer to the result of redirection.
This was resolved in relation to the conformance criteria for a POWDER Processor which SHOULD NOT, where IRI1 is in scope of a given DR and dereferencing it redirects to IRI2, automatically treat IRI2 as also being in scope of that DR.
OQ 13:It is not clear how the requirement that each cLabel must have a unique identity, so any modification to it, such as renewing its validity period, will result in the creation of a new cLabel, with a new URI fits in with the operation of large scale workflows, which cannot easily accommodate changes in associations between content and their labels, and consequently this is for further study.
This is covered in the Primer which advises the creation of a 'latest version' link which would redirect to the appropriate POWDER document.
OQ 14:On a related note, the group discussed the relationship between the validity of the label and the cache headers that may be attached to it, but came to no clear conclusion on this. One suggestion is that clients should not be required to use the valid-until date in a cLabel to decide whether to fetch the resource. LA's would be encouraged to use HTTP response cache features, e.g. by setting Cache-Control: max-age to correspond to the appropriate valid-until date.
This issue was resolved and is discussed in Section 5.2 of the Description resources document.
OQ 15:[This section is subject to further review and elaboration - e.g. which terms are mandatory, which are optional, how to provide a unique identifier for the vocabulary. Note also that some of the terms suggest that labels can be altered, and there is an open question as to whether this is in fact possible, given that each instance of a Content Label must have a unique and unambiguous ID. Equally it is important that when a label is 'renewed' that it is not then necessary to change all references to it. It may be possible to work around this by accessing labels by 30x redirection, but the rules applications would be required to follow remain to be discussed ]
The POWDER-S vocabulary is fully defined with a namespace document at http://www.w3.org/2007/05/powder-s. It is a minimal set of terms and classes that can be built on to suit different application environments.
OQ 16:If successful in securing a WG charter, WCL will need to define additional terms for certifying labels. Also, it may be possible to define tests for some of the vocabulary terms.
See Section 5 of the Description Resources document.
OQ 17: If successful in securing a WG charter, WCL would seek to:
— Produce a normative encoding of the WCL model in RDF. This would, of course, take into account any changes made to the model made by the WG itself. The discussion would be likely to include sample SPARQL queries etc. and guidance on making data available for property-based resource grouping.
— Show examples of cLabels encoded using RDFa.
— At least sketch encoding cLabels entirely in XML.
All of these features are present. The Description Resources document encodes the WCL model in both XML and RDF and includes an example of linking to a DR using RDFa. Sample SPARQL queries are provided in the Section 5 of the Formal Semantics document.

Having conducted this review, the working group therefore contends that the open questions posed in the incubator group have been answered.

Phil Archer,
POWDER WG Chair
16 December 2008.

Phil ARCHER
Permalink 01:53:22 pm, Categories: Meeting summaries

Meeting Summary 15th Deceember 2008

The group has now completed its work in terms of defining POWDER. The group is concerned with making sure all the documents are polished and ready for transition to Proposed Recommendation and that the various tools properly implement the different features. An implementation report will be compiled in the coming days. Other documents showing that comments have been answered and issues resolved will also be finalised. The Christmas holiday means it's unlikely that the group will be able to seek transition to PR before the end of the year but will do so in the first working week of 2009. For now the good news is that the weekly telecons are done!
Phil ARCHER

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