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RE: ProjectExpressions without concat

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Tue, 16 Jun 2009 10:07:26 +0000
To: Axel Polleres <axel.polleres@deri.org>
CC: Kjetil Kjernsmo <Kjetil.Kjernsmo@computas.com>, "public-rdf-dawg@w3.org" <public-rdf-dawg@w3.org>
Message-ID: <B6CF1054FDC8B845BF93A6645D19BEA3646CFC687B@GVW1118EXC.americas.hpqcorp.net>


> -----Original Message-----
> From: Axel Polleres [mailto:axel.polleres@deri.org]
> Sent: 15 June 2009 23:28
> To: Axel Polleres
> Cc: Seaborne, Andy; Steve Harris; Kjetil Kjernsmo; public-rdf-dawg@w3.org
> Subject: ProjectExpressions without concat
> 
> Kjetil was concerned since fn:concat wasn't supported yet in standard
> SPARQL. An alternative would be to resort to something else, like e.g.
> STR():

SPARQL/Query 1.0 allows for addition filter functions so fn:concat may not in a standard library but it is legal.  I like the reuse of the F&O function.

The built-in functions in SPARQL/Query 1.0 don't perform much in the way of term introduction (calculation) which is an aspect of the value here.

	Andy


> 
> e.g.
> 
>     CONSTRUCT { ?x ex:mailstring STR(?mbox) . }
>     WHERE { ?x foaf:mbox ?mbox }
> 
> or (using subqueries)
> 
>     CONSTRUCT { ?x ex:mailstring ?m . }
>     WHERE {
>       { SELECT ?x, STR(?mbox) AS ?m
>         ?x foaf:mbox ?mbox
>       }
> 
> but I am quite unsure... is there anyone supporting this?
> 
> I suggest, in the absence of better options
> 
> i) to mention (if implemented) Option 1) first, or alternatively Option
> 4) with reference to XSPARQL
> and then
> 
> ii) We may also want to mention Option 3) as an alternative, with a
> backward-reference to the section on subqueries. Not sure who implements
> both  XPath F&O (i.e. fn:concat) and subqueries, but you could leave a
> TODO there. Anyways, a reference to XPath F&O [XPath-Functions] should
> IMO be added in the references.
> 
> 
> [XPath-Functions] XQuery 1.0 and XPath 2.0 Functions and Operators, A.
> Malhotra, J. Melton, N. Walsh (Editors), W3C Recommendation, World Wide
> Web Consortium, 23 January 2007,
> http://www.w3.org/TR/2007/REC-xpath-functions-20070123/. Latest version
> available at http://www.w3.org/TR/xpath-functions/.

> 
> 
> 
> Axel Polleres wrote:
> > Seaborne, Andy wrote:
> >>
> >>> -----Original Message-----
> >>> From: public-rdf-dawg-request@w3.org [mailto:public-rdf-dawg-
> >>> request@w3.org] On Behalf Of Steve Harris
> >>> Sent: 15 June 2009 12:07
> >>> To: Kjetil Kjernsmo
> >>> Cc: public-rdf-dawg@w3.org
> >>> Subject: Re: Requesting input for the Features and Rational document
> >>>
> >>> On 10 Jun 2009, at 09:42, Kjetil Kjernsmo wrote:
> >>>
> >>>> On Thursday 04 June 2009 08:46:29 Lee Feigenbaum wrote:
> >>>>>> * ProjectExpression needs a better description and motivation.
> >>>>>> We feel that the mention of XSLT is not very relevant, as
> >>>>>> assigning a
> >>>>>> name automatically, like some engines do now, is sufficient for
> >>>>>> XSLT.
> >>>>>> It should also be motivated by showing why it is required by other
> >>>>>> features.
> >>>>> I took a stab at this at
> >>>>> http://www.w3.org/2009/sparql/wiki/Feature:ProjectExpressions

> >>>> As discussed on the teleconf yesterday, it needs better examples
> >>>> too. It
> >>>> doesn't sound like the examples are actually executeable as it is
> >>>> now, and
> >>>> they should be. Also, it is also a good thing if they do not rely on
> >>>> other
> >>>> features that we do not yet have, such as concat().
> >>>>
> >>>> It is good to have both SELECT and CONSTRUCT examples.
> >>>>
> >>>> Can anyone have a stab at this?
> >>>   CONSTRUCT { ?x foaf:name (concat(?fn, " ", ?sn)) . }
> >>
> >> Can we adopt F&O naming here?  It's "fn:concat"
> >> Tricky - () looks awfully like a list to a parser.  Especially if the
> >> function is named by URI.
> >
> > Indeed....
> >
> >
> > Option 1)
> >> Suggestion: off the top of my head: ?(expr)
> >>
> >>    CONSTRUCT { ?x foaf:name $(fn:concat(?fn, " ", ?sn)) . }
> >>
> >> Not necessary beautiful but it will work.
> >
> > Option 2) another options here is to leave it without extra syntax, but
> > add a TODO mentioning that
> >
> >     fn:concat(?fn, " ", ?sn)
> >
> >    is problematic for parsers due to the similarity with list notation.
> >    I.e.
> >
> > TODO: Note that expressions such as fn:concat(?fn, " ", ?sn) are
> > potentially problematic for parsers due to their similariy with the
> > shortcut notation for
> > [http://www.w3.org/TR/rdf-sparql-query/#collections RDF Collections]
> >
> > Option 3) is actually the subselect, i.e. the complete corrected example:
> >
> >  CONSTRUCT { ?x foaf:name ?concat . }
> >  WHERE {
> >    { SELECT ?x fn:concat(?fn, " ", ?sn) AS ?concat
> >      WHERE { ?x foaf:firstName ?fn ; foaf:family_name ?sn . }
> >    }
> >  }
> >
> >
> > Are Options 1) or 2) implemented anywhere?
> >
> >
> > Option 4)
> > If you look for something which is implemented, we have an
> > implementation for a slightly different version of Option 1) in XSPARQL
> > [1]:
> >
> >    CONSTRUCT { ?x foaf:name {fn:concat(?fn, " ", ?sn)} . }
> >    WHERE { ?x foaf:firstName ?fn ; foaf:family_name ?sn . }
> >
> >  I had, BTW, Option 2 implemented in some preliminary,
> > experimental parser for dlvhex-sparql [2], but basically at the
> > cost of sacrificing the collection shortcut notation.
> >
> > best,
> > Axel
> >
> > 1. http://xsparql.deri.org/

> > For the example see:
> > http://xsparql.deri.org/spec/xsparql-language-

> specification.html#fig:rdf2rdf_xsparql
> >
> > Implementation:
> > http://sourceforge.net/project/showfiles.php?group_id=243296

> >
> >
> > 2. Axel Polleres, Fran├žois Scharffe, and Roman Schindlauer. SPARQL++ for
> > mapping between RDF vocabularies. In OTM 2007, Part I : Proceedings of
> > the 6th International Conference on Ontologies, DataBases, and
> > Applications of Semantics (ODBASE 2007), volume 4803 of Lecture Notes in
> > Computer Science, pages 878-896, Vilamoura, Algarve, Portugal, November
> > 2007. Springer.
> >
> >> This is a place where explicit assignment would be useful syntax.
> >>
> >>>   WHERE { ?x foaf:firstName ?fn ; foaf:family_name ?sn . }
> >>>
> >>> As a projection it would be something like:
> >>>
> >>>   CONSTRUCT { ?x foaf:name ?concat . }
> >>>   WHERE {
> >>>     { SELECT ?x, concat(?fn, " ", ?sn) AS ?concat
> >>
> >> SELECT ?x fn:concat....
> >>
> >> (no comma - comma in SELECT lists are in the time permitting query
> >> language syntax.
> >>
> >>>     WHERE { ?x foaf:firstName ?fn ; foaf:family_name ?sn . } }
> >>>   }
> >>>
> >>> - Steve
> >>
> >>     Andy
> >>
> >
> >
> 
> 
> --
> Dr. Axel Polleres
> Digital Enterprise Research Institute, National University of Ireland,
> Galway
> email: axel.polleres@deri.org  url: http://www.polleres.net/


Received on Tuesday, 16 June 2009 10:08:34 GMT

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