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Re: naive question: why prefer absolute URIs to # URIs for linked data?

From: Ivan Herman <ivan@w3.org>
Date: Wed, 31 Aug 2011 15:12:26 +0200
Cc: Jonathan Rees <jar@creativecommons.org>, www-tag@w3.org, Manu Sporny <msporny@digitalbazaar.com>, Harry Halpin <hhalpin@ibiblio.org>, Ian Davis <me@iandavis.com>
Message-Id: <86CB3DA0-8783-4D3A-86AF-050B931506B4@w3.org>
To: Martin J. Dürst <duerst@it.aoyama.ac.jp>

On Aug 30, 2011, at 03:11 , Martin J. Dürst wrote:

> Hello Ivan,
> 
> On 2011/08/29 20:47, Ivan Herman wrote:
> 
>> in my understanding that is related to the follow-your-nose principle. If I see a URI for a, say, predicate, I may want to follow that URI and get some information. That predicate (or class or whatever) is rarely alone, it may be part of a vocabulary.
>> 
>> If the URI is of the form http://blabla#blah, that means that I, typically, have a large vocabulary file at http://blabla and #blah is somewhere there. So if I dereference http://blabla#blah, I will get the full vocabulary and I will have to locate the specific element #blah to something with it (as a caller). If the vocabulary is very large, that might be a pain.
>> 
>> If the URI is of the form http://blabla/blah, and I dereference it then I can expect to get only the information I am looking for.
> 
> That's indeed a potential problem, but not an absolute argument against using fragment identifiers. Just to the contrary, if I'm following my nose to dereference http://blabla#blah, there is a reasonable chance that I might also subsequently want or have to dereference other stuff in the  http://blabla vocabulary such as  http://blabla#foo and http://blabla#bar.
> 
> If I already have downloaded  http://blabla, then these are essentially immediately available, whereas if I have to access http://blabla/foo and http://blabla/bar separately, it will take some time (network access is magnitudes slower than local memory access).
> 
> So the only conclusion from this seems to be a good practice: "When creating vocabularies, organize them in reasonable-sized chunks of closely related terms to avoid having to download a huge document or a large number of very tiny documents."
> 
> Of course, the optimum size and organization of the chunks will depend a lot on network bandwidth and latency and the actual set of terms needed, but what's important here is not to reach the optimum, but to avoid completely inefficient edge cases (every term in a separate document even if closely related, or a single huge file of stuff that rarely is needed together). That's good because even infrequent reorganization would be a bad idea.
> 
> In any case, these considerations clearly seem to support the use of fragment identifiers (into reasonable-sized files), rather than to be an argument against fragment identifiers.

I guess I agree. In my view hash URI-s for vocabularies are perfectly fine for relatively small vocabularies

Cheers

Ivan


> 
> Regards,    Martin.
> 


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Ivan Herman, W3C Semantic Web Activity Lead
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Received on Wednesday, 31 August 2011 13:12:55 GMT

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