POWDER Working Group Blog

The group had a quick discussion about the current state of play which is as follows:

1. XSLT for POWDER-BASE to POWDER - coming along nicely. The basics are done, with a manageable To Do list (ordered lists, tagsets, conflicting descriptions, predefined descriptions). This is an important implementation of the formal doc.
2. The Semantic POWDER processor is done, complete with tarball and help page at http://transonto.sourceforge.net/
3. The second POWDER Processor is expected to be online any day now.
4. The comments received from Michael Schneider and Jonathan Rees need (and will get) a proper answer but the result is that we do not need to substantially change the semantic extension.
5. Tony Hammond's point about the '//' in IRIs being mandatory when they should be optional in the regular expressions is not right as POWDER$ is about HTTP and HTTP-like URI schemes. Other URI schemes can be handled by POWDER but by extending POWDER-BASE.
6. Minor editorial issues are being dealt with.
7. The registration of the Media Types and @rel type is progressing but it's taking quite a lot of effort.
8. The group is fully on track to get ready for a request for a PR transition before Christmas although we may just mis the moratorium. A lot depends, particularly, on whether the XSLT work gets caught by any banana skins along the way.

We're getting there.

The group made a quick review of the various implementations under way at the moment. There are a lot: a validator, two POWDER Processors, one POWDER-S Processor, an XSLT for POWDER to POWDER-BASE is just being debugged, the POWDER-BASE to POWDER-S XSLT is on the way and the deployment of POWDER on a large content portal is due online any day now. Good! But... there's not hiding the fact that all these need a little more work before they reach full release status and, of course, time is running out. The target is to seek transition to Proposed Recommendation w/c 15 December (W3C has a publication request moratorium beginning 18th Dec). The group spent a little time looking at comments received from Jonathan Rees and Dan Brickley. Further answers will be sent to those correspondents but the belief among the group is that the comments received will not need to significant changes to the published documents. The group noted that substantial discussions are ongoing regarding the issue of HTTP Link and relationship type registrations. A new draft of the HTTP Link doc is now published, with relevant threads on the HTTP mailing list and a new one set up by Eran Hammer-Lahav on metadata discovery The bottom line is that there appears to be broad consensus that HTTP Link will return and that the relationship type registry proposed by Mark Nottingham will come into effect. However, this won't be until after the POWDER WG has finished its work so that section 4.1.2 now seems almost certain to be flagged as informative rather than normative. The group also noted the new Internet Draft (also submitted by Mark Nottingham) proposing /site-meta as 'the well known location to end all other well known locations.'

Ah! I've finally got around to updating the blog. Apologies for being rather lax in this regard. The good news is that our 3 Rec Track documents, plus the Primer and POWDER-S vocabulary, have all been updated. See the WG homepage for links. That same page now also has links to running code - with more on the way in the coming couple of weeks. The request to register 'describedby' as a relationship type has been made to IANA (just need to sort out the MIME type request as well). We're only meeting every other week now, so next telecon is due for Monday 1st December. The group is open to Last Call comments through until Friday 5th December.

Almost all of the group's documents are being published today as a Second Last Call (with a signal that the group does not intend to make a separate call for implementations). Among other things this will be a trigger to contact IANA about registering the 'describedby' relationship type and the two POWDER MIME types. Meanwhile progress is being made on various code items:

• The XSLT for POWDER to POWDER-BASE should be available any time now with the transformation from POWDER-BASE to POWDER-S to follow around the end of this week.
• A POWDER-S processor that uses Jena and Pellet exists with code available at source forge but this needs additional documentation before we can point to it as an implementation. There may be one or two minor additions to make as well.
• A POWDER-Processor written in PHP is under development and should be available by the end of the month.
• A (Perl) validator is online now that also does the POWDER to POWDER-BASE transformation. This is very nearly complete will be moved to validator.w3.org before long.
• The transformation function is also available as a separate script.
• Much of the code is also used in a second POWDER Processor.

The important point to note here being that there is a growing body of running code that will be available within the next 2-3 weeks. We remain on target to complete our work and seek transition to Proposed Recommendation before Christmas. The group spent a little time discussing the future of POWDER. Areas such as building the trust model and using POWDER in profile-matching systems are those that seem most likely to be developed in future.

The group took a look at recent work done on a test implementation of adding POWDER to a portal - it all looks solid and another strong case for HTTP Link! We also looked briefly at the work from Korea on a microformat based on POWDER. This is, of course, interesting and is a good indication of what is and is not clear about our work to date. The group will engage directly with Jonathan Jeong on this point. The Rec Track documents are all being finalised this week ready for publication next week. It was decided at the TPAC face to face that we will make a Second Last Call announcement but indicate that we do not intent to make a separate call for implementations (CR). The LC period should end Friday 28 November - giving us enough time to seek the transition to PR before Christmas. We are in touch with the RIF over perhaps including a new informative section in the formal document that would show how POWDER could be expressed in RIF. This will be added if there is time to do so, but this week is the deadline for making any further changes to our rec track documents if we are to hit the bigger deadlines.

We got a lot of work done across the 2 days but it's hard to blog the detail. The time was taken up with line by line discussion of the Primer, POWDER-S vocabulary and our 3 Recommendation Track documents. The end results should be published soon as Second Last Call versions of those documents but with a note that the WG does not expect to make a separate call for test implementations (CR phase) and instead shoot straight for Proposed Recommendation in December.

Following the e-mail discussion, the group formally resolved to 'drop support for arbitrary RDF' in a POWDER document. This means that attribution information must be provided in a separate file, not within the POWDER doc itself; and that descriptor sets will only have terms for which the object is a literal or an RDF resource. This means that the feature at risk flagged in the formal document has been removed. POWDER-S is unaffected. Another issue highlighted in the current (Last Call) documents is that of the range of the issuedby property. After a lot of discussion it has been resolved that the range of the wdrs:issuedby property will be defined as being a class that includes, but is not limited to, foaf:Agent and dcterms:Agent. Resolving this also made clear that a POWDER-S document is an owl:Ontology, not an owl:Thing which has implications for what can and can't be said out it. Finally, we discussed the QA requirements as they relate to the various Rec Track documents. Conformance sections to be added! Activity in the next week should take us very close to being ready to seek transition to CR for the 3 Rec Track documents. A POWDER-S processor already exists (at NCSR as part of the Quatro Project) and at least one POWDER Processor is nearly complete. The group decided at its last face to face that the CR exit criteria would be two POWDER Processors and one POWDER-S processor - so we're well on target.

The main substantive topic of conversation today concerned the issue of whether it was right to use foaf:depiction as an annotation property in a descriptor set class (in POWDER-S) as described by Andrea. The answer is no, it isn't! Hence, it has been resolved that we will define our own term wdrs:logo. The problem does not occur with dcterms:description since, unlike FOAF, dc does not define a domain of owl:Thing for its properties. The group also noted the substantial comments received today from Michael Schneider. These will be answered in the coming days. Finally, the group had a brief discussion about plans for the transition to CR. Preparation for this is due to be completed before the face to face meeting next week at TPAC and the end of CR should fall around the end of November.

No meeting this week - but we're working through the Last Call comments and should be able to resolve most, if not all, outstanding issues this coming Monday (fingers crossed).

The meeting began with a quick review of the Outreach event at Yahoo! and the status of work on implementations (Jena extension to handle POWDER-S seems to be done and two POWDER implementations are well under way). The group's attention must now turn to getting ready to declare its work finished by the time of its next and final) face to face meeting at TPAC next month. The group began to work through the last call comments received. Various members took action items to draft responses with a couple of issues still outstanding (all flagged in the various documents). These are whether or not we will support the inclusion of FOAF/DC Terms info directly in a POWDER doc as well as more complex RDF descriptions in the descriptors. The group is generally minded to drop support for this but arguments are being made to retain them. The issue is likely to be resolved within the next week. Likewise, the issue of whether a POWDER author should be a dcterms:creator or a foaf:maker has still not been entirely resolved. Having decided to make a POWDER doc an instance of an OWL ontology, foaf:maker (which has a domain of owl:Thing) becomes problematic. The semantic heads are thinking this through and, again, we should have this resolved within the next 7 days. Meanwhile, there have been comments on the Primer and work is continuing on the XSLT.

POWDER Outreach Event More of What You Want When You Want It This was the third and (probably) final outreach event organised by the POWDER Working Group. Hosted by Yahoo!, who have long been interested in the concepts around machine-readable trustmarks through this working group and the Quatro Project which is part of the EU's Safer Internet Programme, the event had a healthy WG member/guest ratio. As with previous occasions, the event was held under the Chatham House Rule which means that reporting is restricted, however, it is safe to say that our guests included TRUSTe, Mpower Media, the MPAA, Secure Path, AT&T, Cable in the Classroom, the Center for Media Literacy, Comcast and more. The working group's output and ideas were well received with several expressions of support. The discussion, naturally, focussed on the issue of trust. Can a machine trust a machine? As POWDER makes clear, the answer to that is no. Trust is a judgement of one person by another – what POWDER does is to facilitate that human judgement. Several organisations in the room made it clear that they are actively looking at implementing POWDER in one way or another, either as a full-blown service or as a test bed. Various group members discussed their own implementation plans and, whilst no one would suggest that there is anything other than a great deal of work yet to do, future adoption of the protocol seems set for a good start. As for adoption by the big search engines - it's clear that if and when there is sufficient POWDER data of sufficient quality (i.e. without spam), then they will be pleased to use it. Any future effect of POWDER on things like position in search results will emerge rather than be announced.

The group is getting ready for the next outreach event at Yahoo in a week's time so there's a focus on making things work at the moment. The XML Schemas are being installed in the correct locations and it should be possible to use a validating XML parser to validate any POWDER doc before the outreach event. Meanwhile, there's a validator well under way as well as a POWDER processor; and work is beginning on the POWDER to POWDER-S XSLT. It's not clear at this stage what progress has been made with the work in Athens. Work has started in two other group members' (large) companies and so there should be plenty of implementation experience building over the next couple of months. The group discussed comments received from Peter Patel-Schneider. A full response will be composed this week and discussed internally before being sent - the good news is that the comments do not appear to highlight significant or unanswerable problems with the Formal Semantics document. Other comments received were discussed and, again, full responses will be sent soon. The group took one resolution this week. Work on the POWDER Processor highlighted the lack of clarity over whether the displaytext and displayicon could appear more than once in a DR. Since a DR may have any number of descriptor sets, and OWL (POWDER-S ) doesn't restrict cardinality of properties it's clear that multiple strings and icons may be presented to a user agent. Since it is not clear how a given UA would handle this situation, the Description Resources document will be amended to advise DR authors only to provide one string and one image to display.

This was a holiday in the US so the European contingent had a brief call to ease back into the work after the summer break. First off, of course, there were cheers for the Last Call announcement and publication of initial drafts of the Primer and test Suite. Two issues were discussed. Firstly, that the XML element <issuedby> in POWDER will be transformed into the wdrs:issued by property in POWDER-S. Whilst there remains some uncertainty about what this points to (foaf:Agent or dcterms:Agent or wdrs:Agent which would either be a union of or sub class of the other two), the XML schema and POWDER-S vocabulary are unaffected and so can be updated quickly. Secondly, following on from the last call comment and subsequent e-mail discussion last month, for the time being at least we are going to use 'describedby' as our relationship type and propose two MIME types for POWDER and POWDER-S. These will be text/powder+xml and application/powder-s+xml respectively which we believe to be in line with RFC 3023, section 2 of which includes "If an XML document -- that is, the unprocessed, source XML document -- is readable by casual users, text/xml is preferable to application/xml. [..] Application/xml is preferable when the XML MIME entity is unreadable by casual users." These are not formal resolutions of the group but indicate our current thinking. The issue of @rel registration is being discussed in various groups, not least the Semantic Web Coordination Group.

A little late due to holidays, here's the blog entry I've been hoping to write since about last November - we've reached Last Call! The group is producing a total of three Recommendation Track documents and Last Call comments on these are welcome through to 14th September. The Grouping of Resources document is the oldest of the three and has retained much of its original character from 2007. A critical aspect of POWDER is the ability to define groups (actually now we talk about IRI sets but it's the same beast). The Description Resources document has been through the most substantial changes since its early days although the first example in the document doesn't look so different from the first public working draft version (published nearly a year ago). It's the division between operational and formal semantics, introduced this year, that is the big change between the first and this Last Call version. The development of the two-version approach (operational and formal semantics) lead to the creation of the Formal Semantics document which underpins the other two. This is the one that defines the semantic extension required to make POWDER work in an OWL/RDF environment and confers membership of a class on an IRI if it matches one or more regular expressions. A couple of issues are worth highlighting. Firstly the Description Resources document supports the re-instatement of the HTTP Link Header as proposed by Mark Nottingham. This also impacts on the wider debate about how @rel values should be managed. Mark Nottingham's Internet Draft makes one suggestion but there are other ideas circulating and the way forward is not 100% clear. It is largely this debate that causes us to flag the recommendation of HTTP Link as a feature at risk. In the Formal Semantics document we note a further feature at risk, namely the ability to include arbitrary RDF in a POWDER document. There are strong arguments on both sides and the group will make a resolution based on Last Call comments received. Alongside the Recommendation Track documents, the WG is pleased to publish drafts of its Primer and Test Suite. These will continue to evolve as the group works through Last Call and Candidate Recommendation phases. Finally, the group has announced its latest outreach event. Called POWDER: More of What You Want, When You Want It, the event takes place at Yahoo!'s Mission College Campus in Santa Clara on 16th September.

Apologies for the late posting of this summary The bulk of the meeting was taken up with one issue, largely as summarised in a recent e-mail thread. The group expressed a variety of views - flexibility to meet future uses against ease of implementation is never an easy trade-off to make. In the end it was resolved that support for arbitrary RDF in POWDER documents (i.e. the XML format) would be marked as a feature at risk. If removed it would mean that:

• The issuedby element (mandatory for all POWDER documents) would always link to an external file in which the foaf:Agent or dcterms:Agent information was contained - this could not be embedded in the POWDER doc.
• That descriptors would have to take values that were literals or RDF Resources as their objects - not further nodes.

Only relatively minor changes are necessary to effect this resolution in the latest editor's drafts. POWDER-S is unaffected. With that discussion held, the group briefly reviewed the latest (internal) versions of its documents. With not a little relief it was resolved that, subject to the changes just described being made, the latest versions of the three Rec Track documents (Grouping, Description Resources and Formal) would be the basis of our Last Call announcement. Simultaneously, First Public Working Drafts of the Primer and test Suite would be published. Resolution taken, the group adjourned for the summer. We will reconvene on 1st September - the Monday after the close of the Last Call period.

The group took the opportunity to go through several of its documents in detail over the course of the 2 days, beginning with the Grouping of Resources document. There was a fairly brief discussion about some of the features that have been removed from earlier versions: grouping by property and CIDR block, for example, and the section on redirection. The changes have come about through a series of discussions with their resolution largely driven by practicality and ensuring that POWDER processing remains manageable. One action item not yet completed is an addition to the POWDER processor section of the DR doc to say that whether a particular processor includes redirected IRIs in a group is application-specific. There was discussion about the canonicalisation section. It was agreed that the text should say that where a DR author knows of patterns that might erroneously lead to inclusion of IRIs in their group, perhaps through processing of IDNs, then he/she should add specific exclusions. As a test of the grouping mechanism and its canonicalisation steps, the group looked at a tool designed to implement this. At present, everything except Punycode translation is included in this tool. Even the proposed new top level domains with no subdomain - such as http://example - still fit the model. It was agreed that in/exclude query contains should only be allowed 0 or 1 times in line with more or less all the other POWDER IRI constraints. The group then moved on to discuss the Description resources document. This prompted a wide ranging debate about various issues, only the most substantial of which are discussed here. In recent e-mail exchanges it was decided that POWDER would support both foaf:maker and dcterms:creator but that our examples would almost all show the dcterms:creator version. This discussion continued at the face to face and in the end it was resolved that we would define our own term of 'issuedby' as both a POWDER element name and POWDER-S property. In the latter case it will be a sub property of both the FOAF and DC properties so that authors are free to use either foaf:Agent or dcterms:Agent classes. The next substantive debate concerned how we handle some specific properties in the descriptor set. In general, properties in POWDER descriptor sets are transformed into property restrictions in the OWL class that takes the place of the descriptor set. This is inappropriate for some commonly used RDF and RDFS properties. As a result we will define POWDER element names of typeof, seealso, comment and label that will be transformed into rdf:type, rdfs:seeAlso, rdfs:comment and rdfs:label annotations respectively. Recognising that authors may, through habit, write these terms in a descriptor set anyway, the transform will also pick up on these properties and render them as if the element names had been used. In other words, you can do either and the POWDER transform will handle it. The next question was "should it be possible to process POWDER without having an RDF processor?" Most of our examples show that the DR author is described in a separate file (these days commonly a FOAF file). Allowing that information to be embedded in a POWDER doc as shown in Example 2-2 strongly suggests that you will need an RDF parser in your POWDER Processor. Requiring an external reference lifts that requirement in some situations. However... a descriptor set can include arbitrary RDF (subject to certain restrictions) so the RDF parser is already required. End result - given that POWDER transports RDF - the group recognises that being able to process POWDER documents implies at least some ability within a POWDER Processor to parse and process RDF. Day 1 ended and day 2 began with a discussion around the abouthosts element. The semantics of it are far from simple - POWDER would be a lot simpler without it, however, it plays too important a role to be dropped so we have to handle it. That said, it should only be used by DR authors where it is necessary and a warning to this effect will be added to the DR doc. The group discussed the POWDER Processor at some length, particularly how they should handle abouthosts and how errors should be reported. There are two basic types of error that a PP may detect: errors in the data and errors in the processing. We assign the error code 100 and 200 to these respectively and suggest that specific implementations can then create their own error codes in the 1xx and 2xx ranges. To support this there'll be 3 new wrds properties: data_error, proc_error and err_code. These will be used in the RDF returned by the POWDER processor (PP) and where there is a data error, the triples will be 'about' the data source and where there is a processing error the triples will be 'about' the processor itself. One specific error, number 101, is defined to report that a DR refers to a descriptor set in another document that sets an abouthosts value which is not in the scope of the DR. The full list of conformance criteria for a PP was agreed and will be in the next version of the DR doc. There was some discussion around the issue of linking resources to POWDER docs. The DR document is OK as is but we have some follow up work to do to make sure that the @rel type of powder is registered/recognised. This will involve liaison with various groups and individuals. The group was joined briefly by Dan Appelquist who was able to confirm the Mobile Web Best Practices Group's requirements for mobileOK. A full example of this will be included in the next version of the DR doc. The discussion of the DR doc came to a close at that point. Changes arising from the discussion will be made in the coming days. Attention turned briefly to the Formal Semantics document. Ivan Herman has made several comments some of which have in fact already been addressed in an as-yet unpublished update but there was significant discussion going on between Ivan, Jeremy Carroll and Stasinos Konstantopoulos (i.e. the people best-able to discuss the detail) and the F2F participants left the formal doc untouched for now. The strong hope is that the next group telecon will resolve to publish updated versions of the Grouping Doc, DR doc and Formal doc. At least the first two of these (and all being well, all 3) will be the Last Call versions. Attention then turned to the Primer. This will be a Group Note and is more or less ready for First Public Working Draft now. The group discussed the existing content and what had to be put in place before FPWD. This amounts to an update of the various examples to match changes in the other documents and adding some place holders for further sections. POWDER has evolved into a complex technology and so the Primer has to tread a fine line between making the it overly complex (and so off-putting for potential users) and over simplified (and so becoming less useful). Over the course of the 2 days it was agreed that the group home page should contain links to other resources produced by group members and others - the Primer is there to stimulate interest in what POWDER can do and how it can fit in with real-world situations and then point readers to the relevant specification documents. The hope and expectation is that a first public working draft can be ready at the time of the Last Call announcement on the Rec Track documents. The final document reviewed by the group was the Test Suite. Again, this is very close to FPWD standard and should be published alongside the Last Call announcement. The aim is to provide tests to match each MUST/MUST NOT statement in the Rec Track documents. Many are already defined in the Test Suite. Like the Primer, this document will end up as a Group Note. The face to face meeting finally turned its attention to the timeline for the remainder of its charter (the end of 2008), Candidate Recommendation Exit Criteria and forthcoming key dates. In brief, it is expected that the formal exit criteria will be two independent implementations of a POWDER Processor and one implementation of the Semantic Extension. The latter will be created in Java and offered as an extension to Jena. Several WG members are planning implementations of various kinds that will demonstrate POWDER's key features: DRs DR lists External Descriptors Links to POWDER documents Trust mechanisms Resource Grouping The Semantic Extension The transformation Important dates in the calendar are: Last Call period on the three Rec Track documents will end on 29 August 16th September - POWDER outreach meeting at Yahoo!'s Mission College Campus in Santa Clara, California. This is open to anyone but registration will be essential. 25th September - demonstration of POWDER in the European Quatro Plus project at the Safer Internet Forum, Luxembourg. The group does not expect to have met its CR exit criteria by then but to have made significant progress towards it. 20 October - TPAC. The WG hopes to use its meeting time to review CR Exit criteria and generally tidy up before seeking transition to Proposed Recommendation. This is a tight schedule but reflects the fact that the group has already well exceeded its original charter and is anxious to complete its work within its extended charter period. Finally, the group thanked its host (Kevin Smith of Vodafone). It was a productive meeting!

The group reviewed the current status of its publications. The DR and Grouping doc have both been updated recently and the Formal Semantics document has been published as a first working draft. The various XML schemas are in place too but not (yet) the POWDER-S vocabulary. It is anticipated that all the namespace documents will be in place before next week's face to face meeting in London. The group then looked at and resolved some relatively minor outstanding issues. 1. Taking note of comments from Masahide Kanzaki and Ivan Herman the erroneous references to rdf:nodeIDs in all POWDER-S examples will be fixed. 2. That there will be a possible child element of descriptorset will be typeof that will take a ref attribute, the value of which is the URI of a Class. The semantics will be that all members of the IRI set will be instances of the referred to class. 3. A longer discussion centred on whether and how to transport XML metadata within POWDER. It was eventually resolved that the group does not need to change or add anything to make this possible since RDF already supports the concept of an XML Literal as an object of a triple. However, an example will be given in the Primer for how to do this. The group also discussed the Primer and Test Suite documents - progress is being made with both of those. The target for the face to face meeting in London next week is that the Grouping, DR and Formal doc will be ready for Last Call, and all other documents, including the Test Suite and Primer will be in the public domain as drafts.

Oops... I've been rather remiss in posting the meeting updates. The next three posts are those for the last few weeks, all of which say things like "the group expects to publish new versions of the document any day now." OK, as I write they really are being installed and the W3C webmaster is making final adjustments... More soon.

The group is working towards getting its already published documents updated and ready for Last Call which, all being well, will be announced at the end of this month. New versions of the Description Resources and Grouping documents are being put through the W3C publication process, along with the new Formal Semantics document. In addition the XML schemata and datatype definitions necessary for POWDER and POWDER-BASE are ready to go along with the POWDER-S RDF vocabulary. These have the appearance of ancillary documents however they are crucial as they are what will make the Protocol for Web Description Resources actually work! The meeting this week spent most of its time, however, looking at two documents that are not quite ready for publication yet - the Primer and test suite. It was felt that we need to have more examples of POWDER processing ready to include in the Primer before it can be published - hopefully around the end of next month. A Test Suite is also being prepared. Some sample data has been prepared and the format of the suite worked out. This week will see specific references to sections of the normative documents included so that it is clearer exactly what the test is about. It is hoped that the Test Suite will be ready for First Public Working Draft by this time next week - when the aim is to announce Last Call on several documents.

This was a relatively short meeting but an important one as we have reached a significant milestone in the group's work. With the exception of the use cases, new versions of all the POWDER documents currently in the public domain are ready to be published, along with some new ones. These include a new Formal Semantics document, XML schemata and RDF vocabulary namespace documents. Work on the Primer and Test Suite is also progressing well and these should be ready at the end of the month when the group plans to make a Last Call announcement on its major Recommendations Track documents.

The bulk of the meeting concerned the Primer which the group intends to publish in the near future as a first public working draft and evolve over the remainder of the year as a Note. It explains why and how to use POWDER and is meant as a general introduction to the whole protocol. Technical detail is included where necessary but is introduced in a near tutorial style. There are a number of open issues but these are being reduced and FPWD should be ready next week. The group resolved to publish an updated working draft of the Description Resources document and seek permission to publish a FPWD of its Formal Semantics document. Meanwhile, updated versions of the schema and vocabulary documents are close to being ready to publish. The Test Suite and an updated version of the Grouping of Resources document should also be ready for the group to resolve to publish on next week's call. The WG was pleased to note the recent discussion in the TAG concerning the HTTP Link Header which is very positive for POWDER.

The detail in several of the group's documents were discussed today, in particular the new one concerning the formal semantics of POWDER and the Test Suite, both of which should be published as first working drafts very shortly. More than ever, each document depends on detail in another. Meanwhile work is progressing well with the XML Schema and datatypes that will aid the validation of POWDER docs. The first half of the meeting picked up on the recent e-mail exchanges [member only link] concerning the formal semantics model. The outstanding questions come down to things like: how important is it to be able to process non-Web URIs? Does a POWDER Processor necessarily have to support an extension mechanism such that it can process any POWDER-like document if the extension is declared properly or is it OK to require additional code? And is grouping by IP address and port number essential? If the answers to all these is no then it all gets much easier so, with time running out for the group, decisions need to be made about what really is essential and what is a nice to have. Many of these issues are really only coming to light as we tie down the details and start to work out actual tests we'll need to pass ourselves (never mind anyone else!). It was the Test Suite that filled most of the remainder of the meeting. What exactly are we testing? It seems that there are two 'products' to test: the POWDER to POWDER-S transform and the POWDER Processor. We need to be clear about the difference between the Test Suite and Candidate Recommendation phase. A document that discusses the sub divisions of specifications looks highly pertinent to both the formal semantics discussion and the Test Suite development. The suggestion was made that as well as providing test data we should also provide examples of predictable mistakes and how processors should handle them - the problem is that it's an open ended question and this seems unlikely to be included in the Test Suite.

The group discussed the concept of 'a POWDER Processor' and agreed that such a thing needs to be defined. As a minimum a POWDER processor will handle two functions: For a given URI u, the function describe(u) will return RDF/XML that has u as the subject. For a given description, d, the function resourcesWith(d) will return one or more regular expressions, all of which must match for a resource to be described by d. There are many options that can be added to this - describe using a given dataset, only use DRs from particular creators etc, returning DRs relevant to the query and so on. Many of these options will be documented but only the two core functions will be mandatory. The group then turned to discussion of the work done recently by Stasinos Konstantopoulos. Subject to consultation outside the group, this work will become a separate new document called POWDER: Formal Semantics. This will underpin the semantics of POWDER-S which in turn will underpin the 'native' POWDER. This creates a 3 layered approach, however, the 3 layers all build on each other. Only POWDER and POWDER-S need be implemented, but the formal semantics, although largely theoretical, provide a benchmark against which the other two can be tested. Since a lot of work has been done in this area already, it will not add significantly to the group's workload. Finally, subject to final confirmation, the next face to face meeting will be on Monday 14th - Tuesday 15th July in London.

The meeting began with a discussion on the Primer document. Many members took action items to begin to create sections of the document that will exemplify their intended usage of POWDER. Early versions of these sections should be in the first public working draft which is due for publication within the next few weeks. There was then a discussion about the processing of URI components that don't lend themselves to regular expression matching - namely port numbers and IP addresses. WG members are working on this and it is hoped that the number of semantic extensions - i.e. RDF/OWL uses that regular tools can't process - will be kept very low. The group also looked at the wisdom and desirability of making the XSLT that enacts the GRDDL transform 'smart'. Should it only insert owl:intersectionOf and owl:unionOf where it is necessary to do so or remain simple with the result that POWDER documents will often include intersections and unions of single classes? Since the meaning in OWL is unchanged and the Semantic POWDER documents are not intended to be produced or read by humans, it was decided to Keep It Simple - and accept extra verbosity even where it's not required, noting that such extra lines may be removed if so desired. Finally, the issue of a conformance section in the grouping doc was also raised - i.e. the lack of one at present. This may need to be added to satisfy Quality Assurance criteria. The group continues to work hard towards a Last Call announcement. The next versions of the grouping and DR docs to be reviewed at next week's meeting and published shortly thereafter should be very close to, if not the, Last Call versions.

This was the first conference call the group has had for a couple of weeks and a lot was discussed. First of all it was agreed that a POWDER processor MUST understand and process POWDER and MAY do this by processing POWDER-S. Publishing POWDER-S is, of course possible, however, this should be done with caution since its processing requires understanding the semantic extensions (i.e. although it's valid RDF/OWL it doesn't mean as much if you don't implement the extensions mapping strings to URIs etc.) Publishing POWDER-S directly may not therefore have the desired semantics. The group then spent time looking at the Primer which, it is strongly hoped, will be published as a first working draft at the end of this month. There was some discussion following comments made on the public list [1 2] and a new internal draft is in preparation. The group is looking into whether it might be appropriate (and helpful) to include examples of using real world vocabularies (to describe fictitious Web sites), e.g. Dublin Core, Creative Commons, ICRA etc. Those examples are all non-profit - would it be appropriate to give examples using commercial vocabularies such as (WG members) Technosite and Segala?. There was a brief look at the HTTP Link issue which is raging on the TAG mailing list. The group was pleased to welcome Tim Boland of NIST to its membership. Tim brings a wide range of skills, experiences and interests to the group from fields including XML technologies, Quality Assurance and Accessibility. For this meeting, we were also joined by Eric Eric Prud'hommeaux who offered further advice on the issue of IRI canonicalisation. This is clearly a many-faceted topic. IRIs are defined, IRI -> URI is defined, HTML form encoding is defined and so on, but where is it appropriate to use each? It seems that the POWDER approach is likely to end up suggesting that processors make a 'best effort' to canonicalise IRIs within the context in which they operate - and this may lead to false negatives. The group is grateful to Eric for offering to continue supporting this aspect of our work. Finally, an important Resolution was passed, congratulating Andrea Perego and his wife, Barbara, on the birth of their son Alessandro!

The group discussed a number of issues related to its charter, in particular the proposed timeline of Last Call on the grouping and DR docs by end April allowing transition to CR before the summer break. The Primer and Test Suite should be in the public domain, although not as far advanced by end April too. This presents the group with a lot of work to do and we must be mindful of what is practical within that time frame, however, the pieces are coming together.

The group is beginning to plan a face to face meeting in June to go through Last Call comments, probably in Darmstadt hosted by Deutsch Telekom. We will need to avoid a clash with the Mobile Web and Voice Browser meetings that month.

Specific topics: how we will document the rules for transforming POWDER into POWDER-S. Various options have been proposed including some sort of formal rule language or detailed documentation within the XSLT. The group resolved to include a natural language description in the documents and provide both the XSLT and the Test Suite - which should be ample material to allow an independent implementation of a transformation engine.

The general rule for the transformation is:

ref -> rdf:resource,
string -> literal (possibly typed),
elements assumed to be embedded RDF/XML.

That is, if you want something to end up as a rdf:resource, encode it in the XML as a ref and so on. RDF/XML may be embedded within the POWDER Doc.

We also briefly discussed the proposal that all IRI constraints should be expressed in POWDER-S as regular expressions. This will minimise the number of extensions needed to existing RDF/OWL tools. Implementing the full set of IRI constraints would require much more work in such tools.

The POWDER WG held its second outreach event on 18th March, hosted by the GSM Association. The event provided an opportunity for our guests to learn what POWDER is and how it can help to delivery more targeted, personalised content to the benefit of content providers and consumers alike. Carl Taylor from Hutchinson Whampoa gave a positive assessment of the technology but warned about the problems that slow adoption could pose and the task ahead to convince content providers of the benefits of adding metadata, no matter how trusted and useful it may be. Another guest, Scott Rose from Arqiva, talked about the difficulty, cost and therefore resistance to adding metadata to large repositories of video – something that POWDER is designed to streamline by allowing data to be applied to many different resources at once.

As well as a series of short presentations of the various use cases, Paul Walsh of Segala and Charles McCathieNevile of Opera Software both demonstrated POWDER being used in user-centric applications. Putting on events like this not only helps to spread the word about the technology, it’s also very useful for WG members to get first hand feedback from potential users. The group hopes to organise further outreach events later in the year.

The following presentations from the event are available as PDFs:

• Carl Taylor (Hutchinson Whampoa)
• Phil Archer (FOSI, WG chair)
• Alan Chuter, Technosite
• Diana Pentecost, AOL LLC
• Kai Scheppe, Deutsche Telekom
• Kevin Smith, Vodafone Group R & D

A lot of work has been going into preparing new working drafts of the Grouping of Resources and Description Resources documents to reflect the development of the new model. The Description Resources doc should be published by the end of this week (Monday 17th latest) and the Grouping doc no more than a week later. Hurrah! There are some issues we need to address in the Grouping doc arising from the change to POWDER being encoded in XML (with an associated GRDDL transform to turn it into RDF/OWL will formal semantics). In the original documents we used OWL's unionOf and intersectionOf to create complex sets - but this doesn't work in XML so we need to work out how to do that. That shouldn't take too long but we're not ready to put it into a WD just yet. Talking of timelines - the group's charter expires this month (oh how optimistic we were...). We are now seeking an extension through to the end of the year. The group hopes to reach Last Call on its currently existing documents around the end of April with CR to follow before the summer.

The group began by checking plans for its forthcoming outreach event, the agenda for which is now finalised. In view of this event, there will be no telecon the previous day but those WG members present will get together before the meeting. In between now and then, the meeting on 10th March will be held an hour earlier to accommodate US daylight saving time. There was considerable discussion about how POWDER will support free text tags and how these might refer to other resources that help to define what they mean. Each tag will be the content of its own element so that white space can be included, and all tags will be elements within a tag set. That tag set has an optional attribute of 'ref' that takes as its value a white space separated list of URIs which may be anything - documents, encyclopaedia entries, RDF vocabulary terms or POWDER Descriptors elements. The term 'ref' was preferred to the earlier working term of 'mapsTo' since the latter implies an equivalence that is not intended. The final discussion was one of those that sounds trivial but that can take up a lot of time. Since POWDER is now working with XML that gets transformed into RDF/OWL we come against different conventions concerning capitalisation of element names (Class and property names). The convention in XML is that everything is lower case. In RDF/OWL, classes begin with upper case letters, properties with lower case and Camel Case is common. The group resolved that the XML convention would prevail, i.e. that lower case element names would be used throughout and these would be preserved by the GRDDL transform. Feedback will be sought on this point as the Semantic Web community may prefer the transform to respect the RDF/OWL naming conventions. This would be possible but might be more confusing than sticking to a single naming convention throughout. The group is very anxious to publish new drafts of its documents and will be working hard this week so that a resolution to do this can be taken next week.

The meeting this week focussed on one topic - how to apply POWDER where there is no structure in a Web site's URIs that can be used to create meaningful URISets. POWDER is about creating sets of URIs and then describing them - those sets being defined by the host, path components etc. But there are cases where this isn't possible and all one can say is something like 'example.org contains some resources that are blue and some resources that are red.' The danger is in creating two statements that conflict, i.e. 'all resources on example.org are blue' AND 'all resources are red.' After much discussion, it was provisionally agreed that the way around this would be to allow POWDER documents - that is, XML files with a root element in the POWDER namespace that contain an attribution element - not to contain any DRs at all. Rather they can contain simply descriptors elements that are not part of any DR and therefore have no scope. The attribution element MAY however include an aboutHosts element, the value of which is a white space separated list of hosts. If such an element is included, then the data in the document, whether in DRs or just descriptions, can only be applied to resources available from those hosts. Such a POWDER document provides some discovery information - example.org contains both red and blue resources - but does not provide any further information about where on that host those resources are. One would need to look at the resource (or perhaps the HTTP headers) to note a link pointing to a particular description. It's not ideal but a) it does not break the POWDER model; b) it does not lead to the creation of conflicting DRs; c) the expressivity is limited by the (lack of) URI structure across the described resources, not by the design of POWDER.

The meeting began with a brief check on progress towards our next outreach meeting. Invitations have been sent out, the agenda is evolving and all but one speaker has confirmed attendance. At the time of writing, there is likely to be space for a few more guests. The group then turned its attention to the new POWDER model that was discussed at the recent Athens face to face (see Jeremy Carroll's summary and previous entries on this blog). Some questions and answers: Is attribution element mandatory? Group resolved yes. Is maker element within attribution mandatory. Group resolved yes (which, as an aside, retains POWDER's dependence on the FOAF vocabulary) Why is the attribution element outside the DRs now? Because it's the only way to make statements about triples without using either reification or named graphs, both of which are unsafe for various reasons. So how can you have DRs with different attribution? By having multiple POWDER documents (and it's worth noting that one POWDER package may link to DRs in other POWDER documents). What about the human-readable text and/or icon - they need to be associated with a DR, not the document. True! Are descriptors RDF predicates and objects or XML attributes and values? Both. Literal values can be encoded either way, but where the object is a URI it must be encoded using the rdf:resource="..." attribute. It's probably better and less ambiguous to use RDF/XML notation for the descriptors. Actually, only the URISet is constrained - this must not include any element from any namespace other than POWDER. Development of the XML Schema for POWDER will be influential here. The conversation then moved on to look at the problem of 'switchable DRs' or cascading DRs. One solution was proposed and found wanting. We're still looking at how to enable a resource to include a link to a DR that describes, perhaps overriding a description already in cache. There was a brief discussion of the group's timeline: the expectation is of new draft documents being published very soon and the hope of reaching Last Call at Easter. Note - the WG includes several Greek members - so Easter may be according to the Orthodox calendar! We will need to seek a charter extension. Finally, e-mails received on the public list were acknowledged.

Several members of the Working Group gathered at the Institute of Informatics and Technology, part of NCSR "Demokritos," for this 2 day face to face meeting and were very pleased to welcome guests Irini Fundulaki of FORTH, Giorgos Stoilos of NTUA and HP's Jeremy Carroll who attended in his capacity as the OWL 1.1 WG's liaison to POWDER. Substantially as a result of Jeremy's input at the meeting and beforehand on both the GRDDL and POWDER mailing lists (with significant input from David Booth) the meeting has agreed a new representation of Description Resources. This will be written up in new drafts of the POWDER technical documents as soon as possible, with publication expected within two weeks or so. In brief, a POWDER document will be written in XML with a root element in the POWDER namespace. The format of such a document will be similar, but not identical, to that already proposed. These documents encode the operational semantics of POWDER – attribution, scope and description – and may be processed in a non-semantic environment. Critically, however, a GRDDL transform associated with the POWDER namespace, when executed, will create an RDF/XML instance with formal semantics that underpin and effectively define the operational semantics of POWDER. Two semantic extensions will be defined. The first will relate a string of the form "http://example.org" to the superficially similar URI <http://example.org>. The second defines the semantics of the white space-separated lists of strings envisaged in the Grouping of Resources document so that they can be interpreted as components of a URI. Thus, the following example can take on the intended meaning of the set of URIs that have a host component with a first and second level domain of example.org or example.com: <wdr:includeHosts>example.org example.com</wdr:includeHosts> More details will be presented in the technical documents, however, the general approach is now agreed. It meets the difficult challenge of creating a system that can work in the day to day, non-semantic web scenarios envisaged in the use cases whilst allowing the data to be processed within a semantic web environment. Several other issues were discussed, such as potential implementations, the test suite, exit criteria for Candidate Recommendation and so on, but the headline from the meeting is clear. After a period in which the group's fundamental approach has been questioned (and was very nearly jettisoned), there is a feeling that the work is back on track. The group records its thanks to NCSR for hosting the meeting, welcomes the interest from its guests, and records its gratitude to Jeremy Carroll for his insight and clear explanations.

We talked briefly about the work that Jeremy Carroll has been doing (and continues to do). It looks very promising and should solve a lot of the problems we have been facing. There was some concern about the limited expressivity of the POWDER Lite document and whether this really means that any complicated Resource set (URI set) must be defined using regular expressions but this doesn't seem to be the case. Also, is the power of OWL being lost? Not really since any DR can be GRDDL'd into an OWL instance. After a bit of housekeeping regarding registrations for the forthcoming face to face in Athens and the outreach event in London in March, we wrapped up early.

The Bristol meeting held just before Christmas means that the group has had a good deal of (very welcome) input from outside its membership. The group digested the advice received so far and actions have been assigned that should bring the Grouping of Resources document and the accompanying vocabulary and schema documents up to date. It seems that the changes necessary for these documents are relatively few in number so we're hopeful of making progress towards last call with these in the near future. In discussing the comments raised by Jeremy Carroll concerning groups of URIs rather then groups of resources, it was resolved that "The WG is happy to forego grouping by resource property if that means that POWDER avoids a lot of complexity for little obvious gain." We'll expand on this in the change log of the grouping doc but the basic point Jeremy makes is taken. The meeting ended with brief discussions about the logistics for the forthcoming face to face meeting in Athens (31 Jan - 1 Feb) and an outreach event being planned with the GSM Association for March.

The meeting began with a discussion of the new Open Archives Initiative's Object Reuse Exchange specification. Like POWDER, this seeks to create aggregations of resources. However, the similarity is not as great as it seems at first: resources are included in the aggregation through explicit enumeration; and ORE does not provide a way to apply metadata to members of the aggregation. It allows you to create an aggregation and declare who you are, when (and presumably why) you made the aggregation etc. but it doesn't allow you to say 'all the resources in the set are blue.' The POWDER WG will send a formal response to the OAI in the near future. The group discussed recent and very welcome input from members of the Semantic Web community and the imminent meeting with Jeremy Carroll, Dan Brickley and Stuart Williams. The expert opinion has swung from the model published originally to one based on OWL and reification and in recent posts by Jeremy back to the original. The WG is generally of the opinion that what matters is meeting the use cases and that is more important than developing the Semantic Web. We need to be able to freeze the basic data structure as soon as practical and move on. Work has begun on the Primer which will seek to answer 5 questions:

1. What is it (and why is it better than what I have already)?
2. What can I do with it (as a producer or consumer of POWDER)?
3. What do I need for it?
4. How do I use it?
5. Is there something I need to worry about?

The group agreed that these were the questions it felt should be answered! Finally, the group briefly discussed plans for an event similar to that held in July. This will be held in London, probably on 18th march 2008 with a strong mobile-element. And with that, the group's work for 2007 was over. Next meeting 7 January.