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Re: A use case for graph literals: Schemapedia (ISSUE-5)

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 8 Apr 2011 16:34:19 +0100
Cc: public-rdf-wg@w3.org, Ian Davis <me@iandavis.com>
Message-Id: <C8EDA43C-029F-4F10-AD5C-782641DD126D@cyganiak.de>
To: antoine.zimmermann@insa-lyon.fr
On 8 Apr 2011, at 15:13, Antoine Zimmermann wrote:
>> <my-gbox>  dc:hasVersion<my-gbox/2011-04-08>  .
>> <my-gbox/2011-04-08>  dc:date "2011-04-08"^xsd:date
> 
> This does not tell me what is in <my-gbox/2011-04-08>.

Sorry, I thought that was clear:

<my-gbox/2011-04-08> { ... content goes here ... }

>>> Another question is, how can one specify the differences between two versions of a g-box? For instance, g-box@2011-04-01 extends g-box@2010-04-01 by adding the triples { :x :y :z . :a :b :c .}.
>>> How can I explicit refer to these specific 2 triples if I can only talk about g-boxes?
>> 
>> Make a new g-box containing these two triples, and use some vocabulary to say that A=B+C
> 
> How do you make a gbox containing those two triples?

<name-of-the-g-box> { ... two triples ... }

>>> As other people suggested, I have the impression that there are use cases for identifying g-boxes and use cases for identifying g-snaps.
>> 
>> I assert that all these use cases can be addressed by declaring some g-boxes immutable. One can have use case specific vocabularies that state which g-boxes are mutable and which not. Note that there is an isomorphism between g-snaps and immutable g-boxes.
> 
> Perhaps but you don't say how I define the content of an immutable gbox.

<my-immutable-g-box> { ... content of the immutable g-box ...}

<my-immutable-g-box> a ex:VersionedSnapshot; ex:timestamp "2011-04-08"^^xsd:date

(where ex: is a use case specific vocabulary that we don't have to define in this WG)

>>> :G1 { :a :b :c . :x :y "{:u :v :w.}"^^rdf:gsnap }
>> 
>> I don't understand what this is supposed to mean.
> 
> This is just a TriG document. At the moment, there is no well defined semantics for it, so I'm just using it at a syntax to somehow connect the URI of the g-box (G1) to a certain g-snap (between the outermost curly brackets). The literal inside that g-snap is just a typed literal, perfectly valid in RDF. A system does not necessarily need to understand that specific datatype, but the idea is to interpret this as a g-snap.
> 
>> You cannot write down a g-box. You can only write down a g-snap. The best you can do is saying that a g-box of a certain name has a certain g-snap as its content right now. Having two different syntactic constructs for writing down g-boxes and g-snaps is a confusing mess that solves no problem.
> 
> At some point either you should be able to talk about specific triples in g-boxes or in g-snaps. It is fine for me to have immutable g-boxes to be able to talk about fixed g-snaps, but I still need a way to make explicit the triples inside.

Right. For making explicit the triples inside a g-box (mutable or not), all you really need is the ability to write down <IRI, g-snap> pairs.

Best,
Richard


> 
>> 
>> Best,
>> Richard
>> 
>> 
>>> 
>>> :G1 identifies a g-box which somehow is related^{1} to the g-snap:
>>> 
>>> :a :b :c .
>>> :x :y "{:u :v :w.}"^^rdf:gsnap
>>> 
>>> and "{:u :v :w.}"^^rdf:gsnap is identifying exactly the g-snap:
>>> 
>>> :u :v :w.
>>> 
>>> I can also say:
>>> 
>>> :G1 :earlierVersion [
>>>   :content "{:a :b :c .}"^^rdf:gsnap .
>>>   :atTime "2010-04-01"^^xsd:date .
>>> ]
>>> 
>>> 
>>> ----Footnote----
>>> {1}  I leave the relationship between :G1 and the content inside the curly brackets to a later email.
>>> 
>>> 
>>> AZ.
> 
> -- 
> Antoine Zimmermann
> Researcher at:
> Laboratoire d'InfoRmatique en Image et Systèmes d'information
> Database Group
> 7 Avenue Jean Capelle
> 69621 Villeurbanne Cedex
> France
> Tel: +33(0)4 72 43 61 74 - Fax: +33(0)4 72 43 87 13
> Lecturer at:
> Institut National des Sciences Appliquées de Lyon
> 20 Avenue Albert Einstein
> 69621 Villeurbanne Cedex
> France
> antoine.zimmermann@insa-lyon.fr
> http://zimmer.aprilfoolsreview.com/
Received on Friday, 8 April 2011 15:34:47 GMT

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