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Re: Dataset URIs and metadata.

From: Frans Knibbe <frans.knibbe@geodan.nl>
Date: Fri, 22 Jul 2011 12:16:13 +0200
Message-ID: <4E294DED.2010603@geodan.nl>
To: public-lod@w3.org
Hello Michael,

On 2011-07-22 10:59, Michael Hausenblas wrote:
>
> Frans,
>
>> I had a quick look. But I could not find it. I had a closer look now 
>> and I see the URI probably is http://dbpedia.org/void/Dataset. I have 
>> tried it. Redirection to either HTML or RDF seems to be in place. 
>> HTML request lead to http://dbpedia.org/void/page/Dataset, which 
>> shows a table of VoID properties. The RDF redirection (to 
>> http://dbpedia.org/void/data/Dataset.rdf) does not seem to work, I 
>> get an error.
>
> Sorry, you lost me here. Did you curl it or how did you get your 
> findings?

Yes, I tried curl. I have just tried it again:

curl -H "Accept: application/rdf+xml" 
http://dbpedia.org/void/data/Dataset.rdf

The response seems to be different from yesterday. Yesterday I 
immediately got an error message. I am afraid I don't have the exact 
message any more. The response I get now is different, a transaction 
time out, which I get after waiting a bit.

Probably this is just a temporary situation and besides the point too.
>
>> Apart from the error, somehow this is not what I expected. I assumed 
>> that the dataset URI is the URI of a dataset. It is the key to all 
>> other data. If you want something from a dataset, you only need to 
>> know this URI. So why is the dataset URI hard to find? Why isn't it 
>> used when references are made to DBpedia? Why isn't it the same as 
>> the base URI (http://dbpedia.org)?.
>
> <http://lod-cloud.net/dbpedia> a void:Dataset;
>                                foaf:homepage <http://dbpedia.org/>;
>
> Says everything, or?
Well, let me see...

First of all, please know that I am new to Linked Data and RDF, so there 
is a chance I don't fully understand everything.

I think what it says is that there is a thing identified by the URI 
http://lod-cloud.net/dbpedia, that that thing is a dataset and that its 
home page is http://dbpedia.org/.

So, does this mean that the URI of the dataset (DBPedia) is 
http://lod-cloud.net/dbpedia??

Sorry if I seem to be stupid, it is not my intention.

>
>> Probably VoID metadata/dataset URIs will be easier to discover once 
>> the /.well-known/void trick (described in paragraph 7.2 of the W3C 
>> VoID document) is widely adopted.
>
> Agreed. But it's not a 'trick'. It's called a standard.
Sorry about that!

Regards,
Frans
>
> Cheers,
>     Michael
> -- 
> Dr. Michael Hausenblas, Research Fellow
> LiDRC - Linked Data Research Centre
> DERI - Digital Enterprise Research Institute
> NUIG - National University of Ireland, Galway
> Ireland, Europe
> Tel. +353 91 495730
> http://linkeddata.deri.ie/
> http://sw-app.org/about.html
>
> On 22 Jul 2011, at 09:42, Frans Knibbe wrote:
>
>> On 2011-07-21 16:27, Michael Hausenblas wrote:
>>>
>>>
>>>> But is this really common practice nowadays? Take DBpedia for 
>>>> example. What is the URI of the DBpedia dataset? Is it 
>>>> http://dbpedia.org? That does not seem to resolve to a set of 
>>>> metadata.
>>>
>>> Did you have a look at the URI I gave you? I mean 
>>> http://lod-cloud.net/void.ttl
>> I had a quick look. But I could not find it. I had a closer look now 
>> and I see the URI probably is http://dbpedia.org/void/Dataset. I have 
>> tried it. Redirection to either HTML or RDF seems to be in place. 
>> HTML request lead to http://dbpedia.org/void/page/Dataset, which 
>> shows a table of VoID properties. The RDF redirection (to 
>> http://dbpedia.org/void/data/Dataset.rdf) does not seem to work, I 
>> get an error.
>>
>> Apart from the error, somehow this is not what I expected. I assumed 
>> that the dataset URI is the URI of a dataset. It is the key to all 
>> other data. If you want something from a dataset, you only need to 
>> know this URI. So why is the dataset URI hard to find? Why isn't it 
>> used when references are made to DBpedia? Why isn't it the same as 
>> the base URI (http://dbpedia.org)?.
>>
>> Probably VoID metadata/dataset URIs will be easier to discover once 
>> the /.well-known/void trick (described in paragraph 7.2 of the W3C 
>> VoID document) is widely adopted.
>>
>>>
>>> BTW, some 30% [1] of the LOD cloud datasets are using VoID ...
>>>
>>>> Is there a general way of obtaining datasets URIs?
>>>
>>> Not to my knowledge. We're working on it in LATC [2] - Keith?
>>>
>>> Cheers,
>>>     Michael
>>>
>>> [1] 
>>> http://www4.wiwiss.fu-berlin.de/lodcloud/state/#data-set-level-metadata
>>> [2] http://latc-project.eu/
>>>
>>> -- 
>>> Dr. Michael Hausenblas, Research Fellow
>>> LiDRC - Linked Data Research Centre
>>> DERI - Digital Enterprise Research Institute
>>> NUIG - National University of Ireland, Galway
>>> Ireland, Europe
>>> Tel. +353 91 495730
>>> http://linkeddata.deri.ie/
>>> http://sw-app.org/about.html
>>>
>>> On 21 Jul 2011, at 15:19, Frans Knibbe wrote:
>>>
>>>>
>>>> Thanks for the replies. It seems that there is agreement that a 
>>>> dataset should have a URI and that dereferencing that URI should 
>>>> return metadata about the dataset. That is good to know.
>>>>
>>>> But is this really common practice nowadays? Take DBpedia for 
>>>> example. What is the URI of the DBpedia dataset? Is it 
>>>> http://dbpedia.org? That does not seem to resolve to a set of 
>>>> metadata.
>>>>
>>>> Is there a general way of obtaining datasets URIs?
>>>>
>>>> I can imagine an RDF dataset comprising all known dataset URIs. And 
>>>> of course that dataset will have a URI itself. Does such a dataset 
>>>> exist at the moment?
>>>>
>>>> Regards,
>>>> Frans
>>>>
>>>>
>>>> On 2011-07-21 12:35, Frans Knibbe wrote:
>>>>>
>>>>> Hello,
>>>>>
>>>>> I have just placed a Linked Data dataset online and now I am 
>>>>> struggling with finding the best way to publish the metadata of 
>>>>> the dataset. I wonder if there are best practices for referencing 
>>>>> a dataset and its metadata, and for linking the two.
>>>>>
>>>>> I did find out that using the Vocabulary of Interlinked Data 
>>>>> (VoID) is a good way to publish the metadata of a dataset. But I 
>>>>> still need some guidance. I have come up with three questions:
>>>>>
>>>>> 1) Is it common practice/recommendable to regard a dataset a 
>>>>> resource? If it is, then all datasets should have a URI, right?
>>>>> 2) If having a dataset URI is a good thing, what should be behind 
>>>>> the URI? Should dereferencing the URI lead to the dataset metadata 
>>>>> (a VoID file for example)?
>>>>> 3) If dereferencing a dataset  URI leads to the dataset metadata, 
>>>>> should there be separate HTML and RDF versions of the metadata? Or 
>>>>> is it better to have a HTML page with embedded (RDFa) RDF data?
>>>>>
>>>>> Thanks in advance for your help,
>>>>> Frans
>>>>
>>>
>>>
>>
>>
>
>
Received on Friday, 22 July 2011 10:16:43 UTC

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