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RE: meaning of (salary, bonus)

From: Mary Fernandez <mff@research.att.com>
Date: 08 Jan 2003 10:07:06 -0500
To: Michael Kay <Michael.Kay@softwareag.com>
Cc: Howard Katz <howardk@fatdog.com>, www-ql@w3.org
Message-Id: <1042038426.1732.63.camel@squeak>


On Wed, 2003-01-08 at 08:33, Kay, Michael wrote:
> 
> > In the *path* expression:
> > 
> >   (salary, bonus)[. > 0]
> > 
> > the resulting salary and bonus elements whose content is 
> > greater than zero will be in document order.  This is because 
> > path expressions always yield sequences of nodes in document 
> > order whereas sequence expressions yield sequences of nodes 
> > in input order.
> 
> No, I don't think this is correct. [] does not cause the sequence it applies
> to to be reordered. The language book has a problem in this area, which I
> will raise on the TF list, but the formal semantics is correct, I believe.

My mistake.  You're absolutely right -- the formal semantics has
it right.   Document order is only 
enforced when a '/' or step occurs in the expression.

So here are the corrected examples:

  (salary, bonus)[ . > 0 ] 

the resulting salary and bonus elements whose content is 
greater than zero will be in input order.


  (salary, bonus)/self::node()[ . > 0 ] 

the resulting salary and bonus elements whose content is 
greater than zero will be in document order, because the
step expression /self::node() yields nodes in document order.

  (salary, 3, bonus)[. > 0] 

the resulting nodes and atomic values whose content/value
is greater than zero will be in input order.

  (salary, 3, bonus)/self::node()[. > 0] 

will raise an error, because the atomic value '3' is not
a node.

I hope my ducks are in a row now.
thx Mary



-- 
Mary Fernandez, Principal Technical Staff Member  
AT&T Labs - Research, 180 Park Ave., Room E243, Florham Park, NJ
07932-0971 
phone: 973-360-8679,  fax: 973-360-8187
mff@research.att.com, http://www.research.att.com/~mff  
Received on Wednesday, 8 January 2003 10:07:23 GMT

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