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Re: Comment about implementation of property paths

From: Jorge Perez <jorge.perez.rojas@gmail.com>
Date: Fri, 25 May 2012 04:07:08 -0700
Message-ID: <CAMAacUAisJXEoNoY=Qe3a5RhtJCLmeNSvF0hvRjSMOA_xDDf9A@mail.gmail.com>
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 GMT

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