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Re: Contd: [pedantic-web] question about sioc / foaf usage

From: natlu2809 <natlu2809@gmail.com>
Date: Tue, 01 Dec 2009 22:40:18 +0000
Message-ID: <4B159B52.1080904@gmail.com>
To: pedantic-web@googlegroups.com
CC: nathan@webr3.org, Linked Data community <public-lod@w3.org>, SIOC-Dev <sioc-dev@googlegroups.com>
Maybe I'm not understanding the dichotomy here:

    * A URI represents a thing, or is an address for a thing
    * Different things have different URIs
    * Different URIs represent different things - the POST, to html
      doc/serialisation, the rdf doc/serialisation
    * URIs are a front for code that generates things

but

    * A URI can represent the same thing in different serialisations
      depending on which agent/device/lense you look at it with

but

    * a different URI can represent the same thing as another URI -
      http://example.lod/doc.html can be the same thing as
      http://example.lod/resource/doc when requested by a html agent ?


The identity however is maintained by the "fingerprint" of the object 
graphs, and the URI is just an image of that fingerprint at some point 
in time/location ?



http:
Kingsley Idehen wrote:
> Nathan wrote:
>> Hi All,
>>
>> To follow on a conversation I'm having with Kingsley at the minute, and
>> to make it public, I'm also cc'ing in public-lod, pedantic-web and the
>> sioc user list, as it is to do with all 3. Please do give feedback and
>> correct me where I'm wrong. Especially if you can inline comment where
>> something is wrong in my understanding.
>>
>> Kingsley Idehen wrote:
>>  
>>> Nathan wrote:
>>>    
>>>> so do / should the Post, HTML Document and RDF Document all have
>>>> different Identifiers?
>>>>       
>>> If you want to make a statement (create a record) describing anything
>>> you need an Identifier for the subject of your description. If you want
>>> said description (a graph pictorial) to be fully explorable using HTTP
>>> (what Linked Data is about) then you shouldn't use the URL (Address 
>>> of a
>>> Resource) as its Identifier. An HTTP GET against a URL has specific
>>> consequences distinct from an HTTP GET against a Generic HTTP scheme 
>>> URI
>>> (a genuine Identifier/Name that Identifies an Object/Resource/Data
>>> Item/Entity).
>>>
>>> Rather than do the whole 303 and hash URI dance (counter productive
>>> since it dances around the issue of Data Identity), see if this 
>>> document
>>> of Data Object Identity clarifies things for you re. Identifiers.
>>>
>>> Links:
>>>
>>> 1.
>>> http://www.cs.cmu.edu/afs/cs.cmu.edu/user/clamen/OODBMS/Manifesto/htManifesto/node4.html 
>>>
>>>
>>>     
>>
>> okay.. here's the set-up; I have:
>>
>> * a "Post" which is a <sioc:Post>
>> * a HTML Document which contains (among other things) a human readable
>> representation of the <sioc:Post> at an URL
>> * a RDF Document which contains a graph pictorial of the <sioc:Post>
>> which is published at an URL
>>
>> to describe or reference the <sioc:Post> I have to give it a URI:
>>   <http://example.lod/uri/post-123>
>>
>> to describe or reference the HTML Document I have to give it a URI:
>>   <http://example.lod/uri/html-document-123>
>> in addition the HTML document has an URL
>>   <http://example.lod/documents/html-document-123.html>
>>
>> to describe or reference the RDF Document I have to give it a URI:
>>   <http://example.lod/uri/rdf-graph-123>
>> in addition the RDF document has an URL
>>   <http://example.lod/documents/rdf-document-123.rdf>
> Assumption: your Identifiers are slash terminated (i.e. Slash style of 
> Generic HTTP URI).
>>
>> now, I'm assuming the RDF Document will need to be self describing (also
>> contain a graph pictorial about itself, as well as the <sioc:Post> -
>> here's a very simplified version of the triples it'd contain.
>>   
> So the RDF data container (resource)  is:
>
> <http://example.lod/documents/rdf-document-123.rdf>, right?
>
>>   <http://example.lod/uri/rdf-graph-123> <rdf:type> <foaf:Document> ;
>>     <dc:title> "SIOC Post profile for post-123"@en
>>     <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>>
>>   <http://example.lod/uri/post-123> <rdf:type> <sioc:Post> .
>>
>> Q1: is <foaf:primaryTopic> correct here?
>>   
> Yep.
>> to say that the <sioc:Post> is contained by this graph we'd add the 
>> triple:
>>   <http://example.lod/uri/post-123>
>>     <sioc:link> <http://example.lod/uri/rdf-graph-123> .
>>   
> Redundant, but not necessarily incorrect. You can make redundant 
> statements :-)
>> then we need to say where the rdf graph can be found (provide it's URL):
>>   <http://example.lod/uri/rdf-graph-123>
>>     <??????> <http://example.lod/documents/rdf-document-123.rdf> .
>>   
>
> <http://example.lod/documents/rdf-document-123.rdf> is a data set 
> container so you identify it properly as in: 
> <http://example.lod/documents/rdf-document-123.rdf#this>, via a simple 
> URL to Generic HTTP URI hack, with Linked Data de-referencing in mind 
> re. exploration of the description of this Thing/Object/Entity/Data 
> Item. Note: a little change-up as I've added a new Identifier but 
> taken the cheap # route via fragment identifier.
>
> This also means your could have stated the following at the top:
>
>  <http://example.lod/documents/rdf-document-123.rdf#this> <rdf:type> 
> <foaf:Document> ;
>     <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>
>  <http://example.lod/uri/post-123> <rdf:type> <sioc:Post>;
>  <dc:title> "SIOC Post profile for post-123"@en.
>
> OR even the following, assuming you'd already assigned these URIs and 
> discovered that <http://example.lod/uri/rdf-graph-123> is basically 
> the same as <http://example.lod/documents/rdf-document-123.rdf#this> 
> i.e., RDF data set containers (documents or information resources):
>
>  <http://example.lod/documents/rdf-document-123.rdf#this> <rdf:type> 
> <foaf:Document> ;
>        <owl:sameAs> <http://example.lod/uri/rdf-graph-123>;
>     <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>
>  <http://example.lod/uri/post-123> <rdf:type> <sioc:Post>;
>  <dc:title> "SIOC Post profile for post-123"@en.
>
>
>
>
>> Q2: which ontology does one use for <??????> in the above triple?
>>   
> None.
>> then we need to say that the HTML document is a document, that contains
>> a human readable version of the <sioc:Post> (amongst other things)
>>
>>   <http://example.lod/uri/html-document-123>
>>     <rdf:type> <foaf:Document> ;
>>     <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>>
>> Q3: is the HTML Document a <sioc:Container>, which is a container of the
>> <sioc:Post>?
>>     <http://example.lod/uri/html-document-123>
>>     <rdf:type> <foaf:Document> , <sioc:Container> ;
>>     <foaf:primaryTopic> <http://example.lod/uri/post-123> ;
>>     <sioc:container_of> <http://example.lod/uri/post-123> .
>>   
> Yes, esp. as <sioc:Post> <rdfs:subClassOf> <sioc:Item> .
>
> Note same applies to the RDF data container as in:
>
> <http://example.lod/uri/rdf-graph-123> <rdf:type> <foaf:Document> , 
> <sioc:Container> ;
>     <foaf:primaryTopic> <http://example.lod/uri/post-123> ;
>     <sioc:container_of> <http://example.lod/uri/post-123> .
>
> OR
> <http://example.lod/uri/rdf-graph-123> <rdf:type> <foaf:Document> , 
> <sioc:Container> ;
>        <owl:sameAs> 
> <http://example.lod/documents/rdf-document-123.rdf#this>;
>     <foaf:primaryTopic> <http://example.lod/uri/post-123> ;
>     <sioc:container_of> <http://example.lod/uri/post-123> .
>
>
>
>> Q4: should we also say the description of the HTML Document is also
>> contained by this graph?
>>   <http://example.lod/uri/post-123>
>>     <sioc:link> <http://example.lod/uri/rdf-graph-123> .
>>   
>
> <http://example.lod/uri/rdf-graph-123> <sioc:link> 
> <http://example.lod/uri/html-document-123>.
> or even: <http://example.lod/uri/rdf-graph-123> <foaf:Topic> 
> <http://example.lod/uri/html-document-123>.
>
>
>> Q5: how do we specify the URL of the HTML Document?
>>     <http://example.lod/uri/html-document-123>
>>     <?????> <http://example.lod/documents/html-document-123.html> .
>>   
> Remember the earlier statement re. the RDF document (resource):
>
>
> <http://example.lod/documents/rdf-document-123.rdf#this> <rdf:type> 
> <foaf:Document> ;
>        <owl:sameAs> <http://example.lod/uri/rdf-graph-123>;
>     <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>
>
> Re. HTML resource description same thing applies re. association with 
> the sioc:Post:
>
>  <http://example.lod/documents/html-document-123.html#this> <rdf:type> 
> <foaf:Document>;
>  <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>
>  <http://example.lod/uri/post-123> <rdf:type> <sioc:Post>;
>  <dc:title> "SIOC Post profile for post-123"@en.
>
> OR
>
> <http://example.lod/documents/html-document-123.html#this> <rdf:type> 
> <foaf:Document> ;
>   <owl:sameAs> <http://example.lod/uri/html-document-123>;
>   <foaf:primaryTopic> <http://example.lod/uri/post-123> .
>
>
>  <http://example.lod/uri/post-123> <rdf:type> <sioc:Post>;
>  <dc:title> "SIOC Post profile for post-123"@en.
>
>
>> I think that's enough for now; all feedback welcome!
>>
>> regards
>>
>> nathan
>>
>>   
> Bar any typos or cut&paste snafus, I've hopefully answered your 
> questions.
> Ultimately, the file (information resource, document, data container) 
> has its own set of attributes e.g. format (dcterms:format), actual 
> file name (not title of the content), creation date etc.. Distinct 
> from the description of its content (hence the use of 
> foaf:primaryTopic as conduit to content description graph).
>
> Link:
>
> 1. 
> http://linkeddata.uriburner.com/about/html/http://news.cnet.com/8301-13577_3-10407056-36.html?tag=newsEditorsPicksArea.0 
> - example of Linked Data graph that describes an document (information 
> resource) in a manner distinct from its content (see the data exposed 
> by foaf:primaryTopic) .
>
>
Received on Wednesday, 2 December 2009 10:58:12 UTC

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