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Re: RDF-ISSUE-111 (dataset-operations): Should RDF Concepts define any operations on RDF datasets? [RDF Concepts]

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Fri, 16 Nov 2012 12:06:24 +0100
Message-ID: <50A61E30.5070208@emse.fr>
To: public-rdf-wg@w3.org
If merge is to be understood in same sense as graph-merge (a logical 
merge), then it is a purely semantic operation. Its definition entirely 
depends on the semantics of dataset.
For instance, if one interprets the graph IRIs as the graph inside the 
named-graph-pair with this name, then there are pairs of RDF datasets 
for which the logical merge does not even exist.

Further, if we define the merge as a purely syntactical operation, then 
the operation may also have the meaning of a logical merge in a 
particular semantics, which in a way would support that the actual 
semantics of datasets is this particular semantics.

For instance, if we define dataset-merge as an operation that 
graph-merges the graphs in the named-graph-pairs having the same name, 
then it is equivalent to a logical merge following the kind of semantics 
that I struggled to defend for a year and a half (while it is 
incompatible with the logical merge of other semantics).


Union and equality have no reason to be defined. Mathematicians have 
taken care of that ages ago. It would not be wise to define union or 
equality in ways that differ from the universally recognised notions of 
equality and union.

Isomorphism is an operation that preserves structure, so it can safely 
be defined independently of the semantics.

Tentative definition:
"""
Two RDF datasets (DG1, NG1) and (DG2, NG2) are dataset-isomorphic iff:
  - DG1 and DG2 are graph-isomorphic;
  - For each (n1,g1) in NG1, there exists (n2,g2) in NG2 such that n1=n2 
and g1 and g2 are graph-isomorphic;
  - For each (n2,g2) in NG2, there exists (n1,g1) in NG1 such that n1=n2 
and g1 and g2 are graph-isomorphic.
"""


--AZ

Le 14/11/2012 12:34, Andy Seaborne a écrit :
>
>
> On 12/11/12 17:37, Pat Hayes wrote:
>>
>> On Nov 9, 2012, at 10:12 AM, RDF Working Group Issue Tracker wrote:
>>
>>> RDF-ISSUE-111 (dataset-operations): Should RDF Concepts define any
>>> operations on RDF datasets? [RDF Concepts]
>>>
>>> http://www.w3.org/2011/rdf-wg/track/issues/111
>>>
>>> Raised by: Richard Cyganiak
>>> On product: RDF Concepts
>>>
>>> Such as merge, union, isomorphism, equality, equivalence?
>>
>> Yes.
>>
>> Pat
>
> +1 (but not too prominently - appendix for graph and dataset operations?)
>
>>
>>>
>>> Things to keep in mind:
>>>
>>> * TriG test cases?
>>> * Anything that SPARQL needs?
>>>
>>>
>>>
>>>
>>
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>>
>>
>>
>>
>
>

-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Friday, 16 November 2012 11:06:54 GMT

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