- From: Axel Polleres <axel.polleres@deri.org>
- Date: Tue, 22 Feb 2011 20:31:54 +0000
- To: "Andy Seaborne" <andy.seaborne@epimorphics.com>
- Cc: "SPARQL Working Group" <public-rdf-dawg@w3.org>
On 22 Feb 2011, at 17:27, Andy Seaborne wrote: > Dataset-UNION is defined to do an RDF merge - it should be set-union. > > Graph store: > DG: { _:a :q :r } > > INSERT { ?x :p 123 . } WHERE { ?x :q :r } > > then we get: > > _:a :q :r . > _:x :p 123 . Hmmmmm, right, but don't we have a more fundamental additional problem there? i.e. isn't the scoping graph (which is used to evaluate the query) only required to be graph-equivalent to the Dataset/Graph Store... From http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#BGPsparqlBNodes "If DS is the dataset of a query, pattern solutions are therefore understood to be not from the active graph of DS itself, but from an RDF graph, called the scoping graph, which is graph-equivalent to the active graph of DS but shares no blank nodes with DS or with BGP. The same scoping graph is used for all solutions to a single query." i.e. that would mean, we'd need to say that - unlike for Query - in Update the scoping graph for any graph in the graph store is that same graph? We probably can - as you suggest - define that in a more precise Definition of Dataset(modify_template,P) which is still fairly hand-waving at this stage (what I am a little worried about is whether a strict definition of the scoping graph locks us in with regard to extending SPARQL Update towards entailment at some later stage...) best, Axel > > because bnodes are not equated in a merge, but are renamed apart: > > [[ http://www.w3.org/TR/rdf-mt/ > if they do share blank nodes, then it is the union of a set of graphs > that is obtained by replacing the graphs in the set by equivalent graphs > that share no blank nodes. This is often described by saying that the > blank nodes have been 'standardized apart'. > ]] > > it needs to be a set union. Constant bnodes are treated by naming > apart, for and every query solution, but not for bnodes arriving by > variable substitution. > > Dataset(modify_template,P) can handle the renaming apart, the > dataset-union can then be a union. > > Andy > > PS The link > > <http://www.w3.org/2009/sparql/docs/update-1.1/definition%20in%20rdf-mt> > does not work. > >
Received on Tuesday, 22 February 2011 20:32:33 UTC