- From: Jorge Perez <jorge.perez.rojas@gmail.com>
- Date: Fri, 25 May 2012 04:07:08 -0700
- To: "Polleres, Axel" <axel.polleres@siemens.com>
- Cc: "public-rdf-dawg-comments@w3.org" <public-rdf-dawg-comments@w3.org>
Thanks Axel, I am really happy with this response. - jorge On Thu, May 24, 2012 at 3:55 AM, Polleres, Axel <axel.polleres@siemens.com> wrote: > Hi Jorge, > > Thanks for reporting on the behaviour of different implementations > regarding property paths and apologies for the delayed reply. > Following the recent re-design of property paths, the group > is currently working on a 2nd Last Call working draft. In the > course of these changes we will also revise our test suite. > Particularly, we have included your suggested test case as > > http://www.w3.org/2009/sparql/docs/tests/data-sparql11/property-path/pp37.rq > > in the test suite. > > As a next step, i.e. to proceed to Proposed Recommendation stage, > we will also solicit implementation reports, to ensure that the > expected behaviours of all features are covered by at least two > implementations. > > We would kindly ask you to acknowledge that you are happy > with this response, > > Axel, on behalf of the SPARQL WG > > --------- > > Hi, > > I just wanted to make an additional comment on this topic before the > LC deadline. The comment is about current implementations of property > paths. > > There are some property path queries that are currently being > evaluated differently by some engines, in particular, KGRAM, Sesame > (2.6.3) and ARQ give different results for the following example. > > data: > > @prefix : <http://example.org/> . > :A0 :P :A1, :A2 . > :A1 :P :A0, :A2 . > :A2 :P :A0, :A1 . > > query: > > prefix : <http://example.org/> > select * where { :A0 ((:P)*)* ?X } > > The following are the results in each case: > > KGRAM: > ------- > | X | > ======= > | :A0 | > | :A1 | > | :A2 | > | :A2 | > | :A1 | > ------- > > Sesame: > ------- > | X | > ======= > | :A0 | > | :A0 | > | :A1 | > | :A2 | > ------- > > ARQ: > ------- > | X | > ======= > | :A0 | > | :A2 | > | :A1 | > | :A1 | > | :A1 | > | :A2 | > | :A2 | > | :A1 | > | :A2 | > | :A2 | > | :A2 | > | :A1 | > | :A1 | > ------- > > > Please notice that my point is not to report a bug in the particular > implementations, but to make an observation on the current semantics. > From my point of view the above example shows that the semantics for > the star (*) operator in property paths is somehow unnatural as at > least three mayor engines that support SPARQL 1.1 evaluate expressions > in different ways. Beside, as far as I know, there is no test case > covering this example. > > Cheers, > - jorge > > > -- > Dr. Axel Polleres > Siemens AG Österreich > Corporate Technology Central Eastern Europe Research & Technologies > CT T CEE > > Tel.: +43 (0) 51707-36983 > Mobile: +43 (0) 664 88550859 > Fax: +43 (0) 51707-56682 mailto:axel.polleres@siemens.com
Received on Friday, 25 May 2012 11:08:17 UTC