W3C home > Mailing lists > Public > public-rdf-wg@w3.org > April 2011

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

From: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>
Date: Mon, 11 Apr 2011 19:48:01 +0200
Message-ID: <4DA33ED1.2070908@insa-lyon.fr>
To: Richard Cyganiak <richard@cyganiak.de>
CC: public-rdf-wg@w3.org
Richard,


Answer below.

Le 11/04/2011 19:34, Richard Cyganiak a écrit :
> Hi Antoine,
>
> On 11 Apr 2011, at 12:47, Antoine Zimmermann wrote:
>> If I have:
>>
>> <a-gbox>   { :x :y :z . :a :b :c }
>>
>> how do I know that<a-gbox>  is referring to exactly those two triples and not to some graph which contains them at the moment (but may change), or even to some graph that entails these 2 triples at the moment?
>
> For your convenience, I'll copy-paste the answer *again* ;-)
>
>>> <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)
>
>
>> If<a-gbox>  is immutable, the relation between the name and the 2 triples must be strict: it has to be exactly those triples, not a superset, not a set which entails them. I understand how mutable and immutable can be handled in the same way, just by taking care that the immutable g-boxes never change. But I do not see how you can do it if the syntax expresses a subset of the underlying graph.
>
> I don't suggest that the syntax should express a subset of the underlying graph. My position is that it should express exactly the graph associated with the IRI.

Ok, in this case, your answer makes perfect sense, but you've certainly 
noticed that this is not a commonly agreed position. That's why I wanted 
to make very clear what you were implying.
I myself hesitate between the various interpretations.


>
> Best,
> Richard
>
>
>
>>
>>
>> AZ.
>>
>>>
>>> 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/
>>>
>>
>>
>> --
>> 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/
>>
>
>


-- 
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 Monday, 11 April 2011 17:48:30 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:25:41 GMT