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Re: First order logic and SPARQL

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 6 Sep 2010 01:54:06 -0500
Cc: Adrian Walker <adriandwalker@gmail.com>, semantic-web@w3.org, public-sparql-dev@w3.org
Message-Id: <14BB6FCE-A76D-46A7-B610-B892F2738988@ihmc.us>
To: Bob MacGregor <bob.macgregor@gmail.com>

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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Received on Monday, 6 September 2010 06:54:41 GMT

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