- From: Enrico Franconi <franconi@inf.unibz.it>
- Date: Thu, 26 Jan 2006 10:38:55 +0100
- To: Pat Hayes <phayes@ihmc.us>
- Cc: "Seaborne, Andy" <andy.seaborne@hp.com>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
On 25 Jan 2006, at 20:42, Pat Hayes wrote: > Wait: G' is not required to be the same graph as G, even in basic > SPARQL. If we do that, then we get compulsory told bnodes for all > conforming engines. So the IRIs and literals in G and G' are the > same, but the bnodeIDs might be (should be, IMO) different. In more > direct language, the answer set can have (has) a different bnode > scope than the dataset graph. We have two options here: 1) The current text says that a standard SPARQL engine (say, of type A) should return the same IRIs as in the original graph. According to my (limited) sampling of the available implementations, engines of type A are the vast majority of existing engines (I found only one not returning the same IRIs, probably done via a post-process of renaming); this shows that actually it is easier for implementations to return the same IRIs as in the original graph (it actually is: it is just a subgraph matching after all). Engines (say, of type B) which do not necessarily return the same IRIs as in the original graph will still be SPARQL-compliant extensions of SPARQL: they have just to declare their different semantics (where G is not necessarily equal to G'). This was the aim of our (successful, so far) game on the parametric semantics: to define a framework were it is possible/necessary to formally define the semantics of the extension in order to be called SPARQL-compliant. This is my favourite choice. 2) The dual option is of course a standard SPARQL where engines (of type B) do not *necessarily* return the same IRIs as in the original graph. This is obtained by deleting the condition that in standard SPARQL G=G'. Engines (of type A) which do return the same IRIs as in the original graph will still be standard SPARQL engines (i.e., engines of type A would be also engines of type B), but users wouldn't know that *in addition* they preserve IRIs names. Engines may *optionally* declare themselves as SPARQL-compliant extensions of SPARQL: they have just to declare their different semantics (i.e., G=G'). This case is bizzarre since after all engines of type A are also engines of type B (the standard ones), so implementors may tend not to declare the different semantics. Andy, what do you think? cheers --e.
Received on Thursday, 26 January 2006 09:39:04 UTC