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RE: Precedence rules for QuantifiedExpr - OrExpr - AndExpr

From: Kay, Michael <Michael.Kay@softwareag.com>
Date: Fri, 19 Dec 2003 18:15:42 +0100
Message-ID: <37B64F4BA60E9E4FB9F60929E059802428776C@DAEMSG03.eur.ad.sag>
To: pgp.coppens@pandora.be, www-ql@w3.org
Cc: public-qt-comments@w3.org

I was rather surprised by this comment, but looking at the way the spec is
written, I can see how you came to this conclusion. I'm pretty sure the
intent was that

some x in y satisfies a or b

should parse as

some x in y satisfies (a or b)

I'm copying it to public-qt-comments so that it gets onto the list of
last-call comments.

Michael Kay 

> -----Original Message-----
> From: www-ql-request@w3.org [mailto:www-ql-request@w3.org] On 
> Behalf Of Peter Coppens
> Sent: 19 December 2003 15:49
> To: www-ql@w3.org
> Subject: Precedence rules for QuantifiedExpr - OrExpr - AndExpr
> 
> 
> 
> All,
> 
> Looking at the XQuery spec, I am somewhat surprised by the 
> consequences of the precedence rules for QuantifiedExpr - 
> OrExpr and AndExpr 
> 
> What I mean is:
> 
> Take the query
> 
> for $x in (1,2,3)
> where 
>   some $y in (1,2) satisfies 1 = $y and $y = 1
> return $x
>  
> Which, I think, is equivalent to 
>  
> for $x in (1,2,3)
> where 
>   some $y in (1,2) satisfies (1 = $y and $y = 1)
> return $x
>  
> But now take the query
>  
> for $x in (1,2,3)
> where 
>   some $y in (1,2) satisfies 1 = $y or $y = 1
> return $x
>  
>  
> Which, I think, is equivalent to 
>  
> for $x in (1,2,3)
> where 
>   (some $y in (1,2) satisfies 1 = $y) or $y = 1
> return $x
> 
> I find that rather confusing.
> 
> So I guess I have the following questions 
> 
> (1) is the above interpretation correct?
> (2) is this a deliberate choice and if yes, are there any 
> motivations for that decision that can be shared?
> (3) would it not be possible to add an extra level of 
> precendence where the OrExpr comes to sit between 
> QuantifiedExpr and AndExpr, or would that propagate to have 
> other side effects?
> 
> Thanks,
> 
> Peter
> 
Received on Friday, 19 December 2003 12:15:29 UTC

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