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Re: Question about "paths as URIs" in the BBC RDF

From: Yves Raimond <yves.raimond@gmail.com>
Date: Thu, 28 Jan 2010 22:44:16 +0000
Message-ID: <82593ac01001281444o6adb33f2l36613564910d980d@mail.gmail.com>
To: Ross Singer <rossfsinger@gmail.com>
Cc: Dan Brickley <danbri@danbri.org>, Linked Data community <public-lod@w3.org>
On Thu, Jan 28, 2010 at 10:09 PM, Ross Singer <rossfsinger@gmail.com> wrote:
> I'm not sure this is what the spec actually says.  xml:base deals with
> relative URIs (which may be either a relative or absolute path, per
> RFC2396 section 5:
> "relativeURI   = ( net_path | abs_path | rel_path ) [ "?" query ]").
>

Then I am getting very confused: shouldn't the example in
http://www.w3.org/TR/2001/REC-xmlbase-20010627/#syntax have /hotpicks/
resolving to http://example.org/today/hotpicks/? Also, according to
the doc Dan mentioned, if it was the case, does that mean something
like "/path" gets resolved to "location of the document/path"?

> I've already mentioned refactoring to take into account 5.1.3, but I'm
> not sure I see the downside to the BBC adding an xml:base declaration.

I'd just like to understand whether there is actually an issue before
fixing it! :-)

Cheers,
y

>
> Thanks,
> -Ross.
>
> On Thu, Jan 28, 2010 at 3:54 PM, Yves Raimond <yves.raimond@gmail.com> wrote:
>> Hello!
>>
>> On Thu, Jan 28, 2010 at 8:36 PM, Dan Brickley <danbri@danbri.org> wrote:
>>> On Thu, Jan 28, 2010 at 7:56 PM, Ross Singer <rossfsinger@gmail.com> wrote:
>>>> Hi, I have a question about something I've run across when trying to
>>>> parse the RDF coming from the BBC.  If you take a document like:
>>>>
>>>> http://www.bbc.co.uk/music/artists/72c536dc-7137-4477-a521-567eeb840fa8.rdf
>>>>
>>>> notice how all of the URIs are paths, but there's no xml:base to
>>>> declare where these actual paths may reside.
>>>>
>>>> If I point rapper at that URI, it brings me back fully qualified URIs:
>>>> <http://www.bbc.co.uk/music/artists/72c536dc-7137-4477-a521-567eeb840fa8#artist>
>>>>
>>>> but the only way I can figure it's able to do that is for the parser
>>>> and the HTTP agent to be in cahoots somehow, which seems like a
>>>> breakdown in the separation of concerns -- this document is useless,
>>>> except in the context of living on www.bbc.co.uk.  The moment I cache
>>>> it to my local system, if I'm understanding it correctly, it's now
>>>> asserting these things about my filesystem (effectively).  Rapper now
>>>> says:
>>>> <file:///music/artists/72c536dc-7137-4477-a521-567eeb840fa8#artist>
>>>>
>>>> So my questions would be:
>>>> 1) Is this "valid"?
>>>> 2) If so, is there an expectation of the parser being aware of the URI
>>>> of retrieval? (I have written my own set of parsers, so I'd need to
>>>> rethink this assumption, if so)
>>>> 3) How do other client libraries handle this?
>>>
>>> Hi Ross,
>>>
>>> The relevant specs are
>>>
>>> http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#section-Syntax-ID-xml-base
>>>
>>> "The XML Infoset provides a base URI attribute xml:base that sets the
>>> base URI for resolving relative RDF URI references, otherwise the base
>>> URI is that of the document. The base URI applies to all RDF/XML
>>> attributes that deal with RDF URI references which are rdf:about,
>>> rdf:resource, rdf:ID and rdf:datatype."
>>
>> This is only relevant for things like rdf:resource="some/path", not
>> rdf:resource="/some/path". In the latter case, the URI will be
>> resolved from the root path, in our case http://www.bbc.co.uk/ (this
>> is the same in the corresponding XHTML pages, btw). I never took a
>> look at the relevant spec (yes, I know, it's bad :-)), but all parsers
>> seem to understand it correctly...
>>
>> As far as caching is concerned, you'd need to parse it and then cache
>> it, not store the documents as is. It would cause issues even in the
>> case of simple relative paths (e.g. rdf:about="#me", as in most FOAF
>> files) not to do it.
>>
>> I hope that helps!
>> Cheers,
>> y
>>
>>>
>>> http://www.faqs.org/rfcs/rfc2396.html which specifies relative URI
>>> processing given a base URI.
>>>
>>> I think most of what you need is in :5.1. Establishing a Base URI" there.
>>>
>>> cheers,
>>>
>>> Dan
>>>
>>>
>>
>
Received on Thursday, 28 January 2010 22:44:51 UTC

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