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Re: Minutes of yesterday's meeting

From: Steve Harris <steve.harris@garlik.com>
Date: Tue, 21 Jul 2009 09:42:08 +0100
Cc: W3C SPARQL Working Group <public-rdf-dawg@w3.org>, public-rdf-dawg-request@w3.org
Message-Id: <E61BFAD8-CC66-4748-B146-6147F67471B1@garlik.com>
To: Simon K Johnston <skjohn@us.ibm.com>
On 21 Jul 2009, at 01:13, Simon K Johnston wrote:

> As mentioned in the minutes I had mentioned last week that in trying  
> to work through the details of MINUS and UNSAID I wonder if one way  
> to get ourselves unstuck is to look at and document some use cases.  
> We do already have NOT EXISTS in SQL (and XQuery) and these are well  
> known and used today so one might ask what they are used for, what  
> queries require these capabilities? For example we might be able to  
> come up with a set of simple queries, expressed in natural language,  
> that we can then evaluate the two proposals against.
> For example, "find me all records where no due date has been set"  
> seems to map well to UNSAID, but seems more clumsy when expressed  
> with MINUS - or rather the natural expression seems harder to read  
> in the resulting SPARQL.

So, I'm not sure I follow this. Probably I'm missing some subtlety in  
"find me all records where no due date has been set", but taking the  
exact keyword out of the equation for a minute I would expect the  
expression to be:

    SELECT ?rec
    WHERE {
      ?rec a :Record .
      UNSAID {
        ?rec :due-date ?date

in either case.

- Steve
Received on Tuesday, 21 July 2009 08:42:49 UTC

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