- From: Andy Seaborne <andy.seaborne@epimorphics.com>
- Date: Wed, 04 Apr 2012 14:10:36 +0100
- To: public-rdf-wg@w3.org
On 04/04/12 13:34, Sandro Hawke wrote: > On Wed, 2012-04-04 at 08:25 +0100, Andy Seaborne wrote: >> >> On 03/04/12 01:27, Sandro Hawke wrote: >>>>> There's some misunderstanding here, yes. Maybe you can talk through >>>>>> > some particular thing you imagine doing, involving merging and TriG, and >>>>>> > I'll be able to pick it up. From what you've written, I'm confused. >>>>>> > >>>>>> > Maybe I can clarifying by translating this TriG document: >>>>>> > >>>>>> > <u1> {<a> <b> <c> } >>>>>> > >>>>>> > into this English declaration: >>>>>> > >>>>>> > The URI 'u1' denotes something, and that thing has exactly one >>>>>> > associated RDF Graph. That associated RDF graph consists of >>>>>> > one RDF triple, which we can write in turtle as "<a> <b> <c>". >>>>> >>>>> >>>>> Clearer, but not what I would have expected. >>>>> >>>>> Why "exactly one associated RDF Graph"? >>> My intuition is that there are important thing you can't do if you allow >>> more than one graph to be associated with the named object, but I >>> haven't really explored that because SPARQL datasets clearly allow only >>> one GRAPH for a given name, so I figured we'd stick with that. That's >>> why I said hasGraph was a functional property. >> >> A query executes at some (idealized) point in time, and a query closes >> the world to execute (or they'd never complete!). An RDF Dataset is >> the local concept for the data being queried - there's no statement >> about anything outside the local context made, or needed for SPARQL. > > I know all that, but I can't figure out what that has to do with whether > hasGraph is a functional property. It's whether the graph is partial or complete-and-closed. Lee's example bring that out; it's also in the earlier "what a TriG doc merge?" Doc 1: <u> { <a> <b> <c> } Doc 2: <u> { <x> <y> <z> } -> merge -> <u> { <x> <y> <z> . <a> <b> <c> } You say rdf:hasGraph is functional -- what is the scope of that? Is it the TriG doc or is it the web? > * Zero or more named graphs. Each named graph is a pair > consisting of an IRI (the graph name), and an RDF graph. > Graph names are unique within an RDF dataset. > Since "Graph names are unique within an RDF dataset", R is a function > (or, in OWL speak: R is functional). All SPARQL says is graph names are unique within an RDF dataset, not on the web. Functional in the mapping name -> graph in the dataset. It makes no statement outside the dataset. But a functional OWL property is functional not just in the graph in which it's used. G1 <a> <functional> <b> . G2 <a> <functional> <c> . merge <a> <functional> <b> , <c> . and conclude <b> owl:sameAs <c> Andy
Received on Wednesday, 4 April 2012 13:11:08 UTC