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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 15:00:57 +0100
Cc: public-rdf-wg@w3.org, Ian Davis <me@iandavis.com>
Message-Id: <AA5CF5B0-66EF-4320-B653-CD35A74EDF63@cyganiak.de>
To: antoine.zimmermann@insa-lyon.fr
On 8 Apr 2011, at 14:29, Antoine Zimmermann wrote:
> how one can say that the content of a g-box at a certain point in time is a certain g-snap?
> If named graphs are in fact named g-box, then how can one relate this name to the content at a certain point in time (for instance, to talk about a certain version of the g-box)?

<my-gbox> dc:hasVersion <my-gbox/2011-04-08> .
<my-gbox/2011-04-08> dc:date "2011-04-08"^xsd:date .

(Or use another vocabulary with stronger versioning semantics instead of DC)

> 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

> 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.

> My opinion at the moment is that we use graph literals for g-snaps (so we don't have to give them names, they are fully defined by their lexical value)

How do I say that a certain unnamed literal g-snap contains 123 triples?

> and we name g-boxes. That is, in TriG:
> 
> :G1 { :a :b :c . :x :y "{:u :v :w.}"^^rdf:gsnap }

I don't understand what this is supposed to mean.

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.

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.
> 
> Le 08/04/2011 14:30, Richard Cyganiak a écrit :
>> Forwarding on behalf of Ian ...
>> 
>> Begin forwarded message:
>>> 
>>> Thanks Richard,
>>> 
>>> A very slight clarification is that the example I gave was from
>>> http://open.vocab.org/ but http://schemapedia.com/ uses the same style
>>> of RDF.
>>> 
>>> An example of one of schemapedia's embedded examples is:
>>> 
>>> http://schemapedia.com/examples/68740744ab36d400d81a1d1af23701e7.rdf
>>> 
>>> Ian
>>> 
>>> 
>>> 
>>> On Fri, Apr 8, 2011 at 11:32 AM, Richard Cyganiak<richard@cyganiak.de>  wro=
>>> te:
>>>> I just had a conversation with Ian Davis on Twitter that yielded a use ca=
>>> se for defining datatype IRIs for graph literals. I thought I'd share it as=
>>>  input into ISSUE-5 [1].
>>>> 
>>>> He uses Turtle snippets as literals in SchemaPedia [2]. SchemaPedia is a =
>>> site that helps find RDF vocabularies, and it lists example usage snippets =
>>> for the vocabularies. The site's back-end is RDF-based. Turtle literals are=
>>>  used to store the examples, as well as change events when examples are mod=
>>> ified. See [3] for a typical change event.
>>>> 
>>>> Currently Ian uses plain literals, because no datatype was readily availa=
>>> ble.
>>>> 
>>>> The idea of abusing Ivan's format URIs from [4] came up.
>>>> 
>>>> Best,
>>>> Richard
>>>> 
>>>> 
>>>> [1] http://www.w3.org/2011/rdf-wg/track/issues/5
>>>> [2] http://schemapedia.com/
>>>> [3] http://api.talis.com/stores/openvocab/meta?about=3Dhttp://open.vocab.=
>>> org/changes/f07ca76699a536dd38b5cbbbe1ba181d&output=3Drdf
>>>> [4] http://www.w3.org/ns/formats/
>>> 
>> 
>> 
> 
> 
> -- 
> 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 14:01:31 GMT

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