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RDFa in XHTML Task Force
28 Jan 2010
See also: IRC log
Manu Sporny, Ivan Herman, Mark Birbeck, Shane McCarron,
1. Action Items
2. RDFa Community Updates
3. RDFa prefix pre-loading
* Summary of Action Items
<manu> ACTION: Manu to create basic RDFa API document. [recorded in
<manu> ACTION: Manu to test CORS support for Pre-loading prefixes in
latest browsers. [recorded in
<scribe> ACTION: Manu to contact Dan Brickley to discuss Microdata
to RDFa mapping. [DONE] [recorded in
Manu: Dan Brickley has been talking to Hixie on WHATWG mailing-list
to see what the overlap between Microdata and RDFa is.
There seems to be a feeling that Microdata is at the very least a
subset of RDFa.
It may be possible to create a profile to use XSLT to map from one
to the other.
<scribe> ACTION: Manu to get in touch with LibXML developers about
TC 142. [CONTINUES] [recorded in
<scribe> ACTION: Mark to generate spec text for @token and @prefix
[CONTINUES] [recorded in
<scribe> ACTION: Mark to generate spec text for pulling in external
vocabulary documents [CONTINUES] [recorded in
<scribe> ACTION: ShaneM to identify the requirements for html2ps and
see about getting reSpec to support them. [CONTINUES] [recorded in
RDFa Community Updates
Manu: Had a chance to read Benji's comments?
... Benji wrote blog-post that was quite critical, some of it
unfairly, of RDFa community.
... He feels that pushing Microdata is a better option for adoption.
... His past posts of the years are along much the same lines, that
the solution should be a collection of tokens, a la Microformats.
... We should take his comments seriously, since he represents an
identifiable set of concerns.
Ivan: We did discuss the possibility of defining Microdata as a
profile of RDFa, and I would be in favour of that.
... But this post talks of removing things that it doesn't seem
possible to remove, such as @resource.
... He doesn't really give an argument for removal.
... Same goes for ranting against CURIEs -- we're working on that
and there's not much more we can say.
... The idea that one set of attribute names is better than another
is really a matter of faith.
... Whilst we don't care that much about the attribute names, a big
problem is existing deployments.
Steven: I've been working on RDFa for at least 7 years, and it's not
as if it suddenly popped out of nowhere.
... It had very thorough discussion, use-cases, etc.
... Microdata comes out of nowhere, but somehow it's presented that
RDFa-proponents are in the wrong.
... Appreciate the work of bridge-building, but we have to remember
that no-one was asking for Microdata.
Mark: I missed the call on Microdata profiles - I think I agree with
Steven, I'm not sure I understand what the benefit is.
Mark: We've been working on this for years and Microdata is in flux
- and is progressively getting closer and closer to RDFa.
Mark: I don't mind the dialog, but we risk damaging deployment if we
change all the attribute names.
Mark: It's sort of religious - one attribute is better than another.
Mark: but there is another way to view this.
Mark: Changing rel to itemprop may be a bad change - @rel and @rev
already has a place in HTML.
Mark: We've been very careful to re-use pre-existing semantic
elements in HTML.
Mark: Microdata duplicates @rel and @rev - so there is a problem
here - that new attributes are being defined for old concepts.
Ivan: Changing attribute names is out of the question.
... On the other hand I don't mind about building bridges.
<Zakim> Manu, you wanted to discuss harm that continued
bike-shedding may cause.
Manu: I'm increasingly concerned about discussions with people like
... The problem was that although we know the background to
Microdata popping up from nowhere, the outside world doesn't.
... They just see a 'fight' going on.
... I think it's harming adoption.
... If others implement a Microdata API in the browser, then that
could affect adoption.
Mark: I don't know if a GRDDL-approach, mapping Microdata to RDFa
would work... we've had that discussion before.
Mark: I think we should focus on RDFa API and getting RDFa out there
<ShaneM> I don't think the transform can be isomorphic.
Mark: RDFa and Microdata are fundamentally not equal.
Mark: This is the same thing that happened with Microformats - RDFa
kept going and I think Microformats are coming to an end soon.
Ivan: Wiki would be a good place to start on some of these ideas.
... (That was response to Mark saying that we should get on and
document some of our ideas on RDFa API.)
Ivan: If as Mark says, that RDFa is superior to Microdata, then we
should be explaining this.
<ShaneM> pre-defined prefixes simplifies immediately
Ivan: If someone doesn't want the full functionality of RDFa it
should be clear how to use it.
Shane would like it minuted that he is paying attention.
RDFa prefix pre-loading
Ivan: At a theoretical and technical level, these things are not
Ivan: They shouldn't need to be presented as being distinct.
Mark: One of the things on the vocab front is this gradual rejection
that follow-your-nose is everything.
Mark: The idea that everything must be able to be worked out on the
fly by default - you need to support follow-your-nose
Mark: But saying that stuff is predefined isn't necessarily a bad
thing - we shouldn't be scared of doing that.
Mark: This is where Microdata and Microformats falls down - they
don't have the follow-your-nose mechanism.
Mark: RDFa does.
Mark: as long as you can ensure that the two co-exist, then why not
<manu> Ivan: Then we largely agree, right?
Mark: The downside to this follow-your-nose is that it is used as an
argument against pre-defined vocabs.
<manu> Ivan: Google uses the same mechanism... but it has been said
all along that a processor would cache a bunch of these namespaces.
<manu> Ivan: caching is a fundamental part of the web.
Ivan: Not disimilar to an editor caching DTDs.
<ShaneM> I want to do this RIGHT NOW
Manu: But which vocabularies would we put into the spec? Which ones
... Top 20 from prefixcc?
Mark: I think we shouldn't be /scared of doing this/ - not /do this
Mark: We should certainly think all of this stuff through... there
isn't a principle that we shouldn't have to pre-define things.
<span property="name">John Smith</span>
Mark: This approach might be better - since it's encapsulated in a
Mark: That is better than Microformats and it's scalable.
Mark: This would allow RDFa processors to understand the URL to mean
Mark: It's a key to tell the authors that their data would be
processed in a particular way.
Mark: Maybe we should defer the pre-loaded prefixes until we can
have this discussion
Mark: Not intending to take the discussion in other direction, just
trying to point out that there may be something even better than
fixing prefix values.
<Zakim> ShaneM, you wanted to talk about the process for picking
Shane: But people forget to use @profile, or they don't have access
to <head>, etc.
<manu> +1 to Shane's comment
Shane: So having the ability to use "dc" or "foaf" without having to
define it, would be very useful.
... Let's just do this now.
<ShaneM> rule one for picking prefixes. vocabs defined by the W3C
Mark: Note that omitting @profile is a red herring.
<manu> how so?
Mark: People raise it, and say that no-one ever used @profile in
<manu> ahh, yes
<manu> I see your point
Mark: But in RDFa if you miss out all the namespaces you're
<manu> The reason they didn't use it was because it had no effect on
Mark: So there's already a basic requirement on authors to add
Mark: Yes, exactly.
Mark: But if you miss out the Google namespace in your RDFa, you
won't get indexed properly.
Mark: Same in Yahoo!.
Mark: So all we're saying is instead of adding 10 URIs, just add
<manu> The #seo people will definitely make a point of it
Mark: A point of getting it right?
Mark: Anyone interested in providing information for some consumer
will want to get it right.
Mark: Control over <head> is a fair point though.
Mark: Shane is right there.
<ShaneM> profile goes on the html element. or the head. I can never
remember. xmlns can go anywhere. and we had a requirement that you
need to be able to do this stuff anywhere.
Mark: Yes, I agree with you there.
Mark: But we also discussed having <div profile="...">
Mark: That would be a nice feature anyway.
Summary of Action Items
[NEW] ACTION: Manu to create basic RDFa API document. [recorded in
[NEW] ACTION: Manu to test CORS support for Pre-loading prefixes in
latest browsers. [recorded in
[PENDING] ACTION: Manu to get in touch with LibXML developers about
TC 142. [recorded in
[PENDING] ACTION: Mark to generate spec text for @token and @prefix
[PENDING] ACTION: Mark to generate spec text for pulling in external
vocabulary documents [recorded in
[PENDING] ACTION: ShaneM to identify the requirements for html2ps
and see about getting reSpec to support them. [recorded in
[DONE] ACTION: Manu to contact Dan Brickley to discuss Microdata to
RDFa mapping. [recorded in
[End of minutes]
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$Date: 2010/01/28 18:46:30 $
Ivan Herman, W3C Semantic Web Activity Lead
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