Re: First order logic and SPARQL

I would say that the mindset "NAF is not appropriate for SPARQL" is a piece
of the explanation for the
glacial pace of adoption of Semantic Web technology in commercial settings.
If indeed SPARQL is
supposed to be religiously open-world (I'm not saying I agree), then IMO
that strengthens the argument for
the adoption of a second RDF language, e.g., something like non-recursive
Datalog with negation, that
is more practical/useful.

Bob

On Sun, Sep 5, 2010 at 11:54 PM, Pat Hayes <phayes@ihmc.us> wrote:

>
> On Sep 6, 2010, at 12:13 AM, Bob MacGregor wrote:
>
> Hi Pat,
>
> On Sun, Sep 5, 2010 at 6:31 PM, Pat Hayes <phayes@ihmc.us> wrote:
>
> On Sep 5, 2010, at 4:48 PM, Bob MacGregor wrote:
>
> > My personal interest is in a query language for RDF that's easy to use,
> and, among other things,
> > has a negation operator that is intuitive.
>
> Id be interested to know what you consider to be intuitive here. Is
> negation by failure intuitive for most Web sources? Do you routinely
> conclude, from a failure to find a sentence asserted on a website, that it
> is false?
>
> Fundamental to your argument seems to be "sentence asserted on a
> website".   If I grabbed
> triples from some random Website, I might not be confident in using NAF.
> But I don't do that.  I work
> with graphs that I've built from sources I trust, and I know which parts of
> the graph are expected to
> be complete, and NAF is perfect for those parts.
>
>
> Well, bully for you, but SPARQL is supposed to be a standard for use with
> RDF on the Web. These nice assumptions of completeness just where you expect
> it cannot be sustained in the wider world of RDF data, and there is no way
> to transmit them (the assumptions) even when they are correct. So NAF is not
> appropriate for SPARQL.
>
> Pat
>
>
> - Bob
>
>
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>
>
>
>


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Robert MacGregor
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