Re: Operations on RDF datasets (ISSUE-111)

On Jan 16, 2013, at 21:00 , Andy Seaborne <andy.seaborne@epimorphics.com> wrote:

> 
> 
> On 16/01/13 18:10, Richard Cyganiak wrote:
>> As discussed in the call today, we need to decide whether to define any operations on RDF Datasets in the RDF Concepts document.
>> 
>> There is a wiki page that lists some possible candidate operations, along with some discussion, pointers to possible definitions, etc.:
>> http://www.w3.org/2011/rdf-wg/wiki/Dataset_Operations
>> 
>> The candidate operations listed there are:
>> 
>> * Isomorphism
> 
> Include for testing otherwise no need.

I am not sure I agree with 'no need': the RDF Semantics does define the equivalence of graphs, I think having a clear definition extended to dataset is, sort of, missing.

Anyway, whatever the reason, I believe this one is a +1 for me.

> 
> The defn quoted in the telecon is fine but clearer if it says "there is a single isomorphism mapping for the dataset", not a separate mapping per graph.
> 
> (which makes it an isomorphism from one set mixing quads and triples to another set)
> 
>> * Union
>> * Merge
>> * Untrusting Merge
>> * Equivalence
>> * Entailment
>> * Equality
>> * Folding/Unfolding
>> * Union Dataset and Merge Dataset
> 
> No need.
> 
> (reason - we don't have time nor want to reopen the dataset semantics discussions)
> 

I am indeed a bit concerned about reopening discussions here. There is also the argument that we should not add things to the standard for which there is no stable community experience yet. 

However (without using telcon time) maybe it is worth considering adding these into the note on Datasets that Antoine is writing. If there is a group who is interested in finding a proper definition for those, that is.

Ivan

>> 
>> Any opinions? In particular, arguments *for* including some of this stuff? Candidate definitions, etc.?
>> 
>> Best,
>> Richard
>> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
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