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Re: CONSTRUCT operator

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 30 Jan 2006 11:30:42 +0000
Message-ID: <43DDF8E2.1090103@hp.com>
To: Pat Hayes <phayes@ihmc.us>
CC: tessaris <tessaris@inf.unibz.it>, RDF Data Access Working Group <public-rdf-dawg@w3.org>

v1.625 hopefully fixes this based on Sergio's option 2.

(I added an SC operator to that is a solution substition followed by 
elimination of triple patterns which still had  variable in them.)


Pat Hayes wrote:
>> Pat Hayes wrote:
>>>>  Moreover, I think that we should adopt a different notation for the
>>>>  variable substitution in graph templates, since it looks the same as
>>>>  the one for BGP but it behaves differently. In particular wrt
>>>>  variables not present in the domain of a pattern solution.
>>>  There once was a tweak in the definition of substitution mapping which I
>>>  think handles this, where S(v)=v if v is outside the domain of S, so S
>>>  maps V to (RDF_T union V). This makes all S's total on templates and
>>>  maps templates to templates (graphs being the special case of templates
>>>  with no variables). Would this handle the issue that you are referring
>>>  to? (If not, I'd like to see an example, because in that case Im not
>>>  following you.)
>> It wont take care of the problem, since by the definition in 10.3.2:
>> """
>> Definition: Graph Template
>> A graph template is a set of triple patterns.
>> If T = { t_j | j = 1,2 ... m } is a graph template and S is a solution
>> then S(t_j) is a set of one RDF triple if all variables in t_j are in
>> the domain of S. S(t_j) is the empty set otherwise.
>> Write S(T) for the union of S(t_j).
>> """
>> triples with variables without assignment "disappear"; while mapping the
>> variables into themselves would generate an RDF graph with variables.
> Ah, now I see what the problem is that you were referring to. OK.
> Pat
>> --sergio
Received on Monday, 30 January 2006 11:31:42 UTC

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