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Re: Na´ve question: Datatypes for RDF Properties?

From: Hammond, Tony <t.hammond@nature.com>
Date: Tue, 09 Dec 2008 15:27:24 +0000
To: Phil Archer <phil@philarcher.org>
CC: <public-powderwg@w3.org>, Stasinos Konstantopoulos <konstant@iit.demokritos.gr>
Message-ID: <C5643EDC.16559%t.hammond@nature.com>

Hi Phil:

Thanks for your answers. I updated the table to take account of both
comments. (Also added in the respective POWDER and ORE mailing lists and
archivesi as a reference convenience.)

I understand that the limitation to authprity-based URIs ("//...") may be be
predicated on pragmatics and appreciate you pointing out the POWDER-BASE
workaround for generic regex'es. (It is a shame though that some URIs are
treated as more equal than others but then that's just a pet gripe of mine.



On 9/12/08 12:49, "Phil Archer" <phil@philarcher.org> wrote:

> Hi Tony,
> Not a naive question at all. I noticed that you'd raised this on your
> blog and added a note to my To Do list to take a look at this. I was
> really pleased to see your ORE/POWDER/sitemap comparison [0] - very
> interesting. I'd been meaning to do something similar and now, joy of
> joys, I don't have to!
> The short answer to your question about data types is yes, POWDER
> supports typed literals - there's no reason not to. The reason we warn
> strongly against anything with blank nodes is that a DR can (indeed
> generally will) apply to resources that don't exist at the time the DR
> was created. This has problems for semantics, see [1]. But that doesn't,
> AFAIK, mean we can't handle datatypes.
> I just created a little example POWDER file with a datatype [2] which
> I'm pleased to say validates. But if I put it through my processor [3]
> the datatype stuff is missed off. This shows that I need to fix a bug in
> the processor, not that RDF datatypes aren't supported.
> If I may, I'd like to answer your other comment [4] while I'm here.
> On the first point, you're right of course. The final version of the
> grouping Doc will not include the colon in the scheme in the cited diagram.
> On the more substantive point about including \/\/ in the template
> regular expressions and therefore making POWDER apply only to IRIs of
> the form scheme://... we discussed this on our call yesterday.
> 'POWDER' has 3 different flavours: POWDER, POWDER-BASE and POWDER-S.
> POWDER is about resources on the Web with IRI constraints defined to
> make group definitions as easy as possible (includehosts,
> excludepathendswith etc.). However, in order to make sure that other URI
> schemes can be used, we introduce an intermediate step between POWDER
> and POWDER-S, known as POWDER-BASE. This only has two elements in an IRI
> set definition: includeregex and excluderegex (in all other aspects it's
> the same as POWDER).
> POWDER-BASE is the key to the IRI set definition extension mechanism -
> any URI can be matched against any regular expression (using the XQuery
> syntax we refer to) and there is certainly no requirement that these
> include ://. The extension examples in the grouping doc [5] include an
> ISAN number for instance. In efect, POWDER is an extension of
> POWDER-BASE: one that's designed to handle HTTP and HTTP-like URIs.
> POWDER-BASE and POWDER-S are much less restrictive.
> Thanks again for your comments - I hope they've answered satisfactorily?
> Phil.
> [0] http://tinyurl.com/5bcsuy
> [1] http://lists.w3.org/Archives/Public/public-xg-wcl/2006Jun/0000.html
> [2] http://keg.icra.org/powder_examples/example_2_1_datatype.xml
> [3] http://tinyurl.com/6zepqu
> [4] http://lists.w3.org/Archives/Public/public-powderwg/2008Dec/0031.html
> [5] http://www.w3.org/TR/2008/WD-powder-grouping-20081114/#extension
> Hammond, Tony wrote:
>> Hi:
>> I have a na´ve question about property values for descriptor sets. From the
>>     "3.2 Descriptor Set Semantics
>>     3.2.1 Descriptor Sets expressed as RDF Properties and Values
>>     A descriptor set contains RDF properties that have fillers that are not
>> blank nodes and that do not identify either a class or a property, ..."
>> This would seem to imply that the RDF properties are simple literals or
>> resources and compound values are not allowed. Is that right? And is there
>> any possibility for datatyping literals?
>> Cheers,
>> Tony
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Received on Tuesday, 9 December 2008 15:28:16 UTC

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