Re: [xml-dev] What class of grammars is an =?UTF-8?Q?XPath=3F?=

[rjelliffe <rjelliffe@allette.com.au>]

 On Thu, 27 Jan 2011 18:06:02 +0000, Michael Kay <mike@saxonica.com> 
 wrote:
>> The particular expression that Michael brought up -- 
>> sum(//order/@value) > 826 -- certainly implies an open language (the 
>> document must have at least one //order/@value).
>
>
> Um, no: the expression is perfectly well-defined on a document that
> contains no orders (it's been a slack week, where are all the
> customers?). There's some kind of implication that the expression is
> designed to work on documents containing zero or more orders, but
> that's all we can say.
 
 ?? If the constraint is that  sum(//order/@value) > 826 must be true, 
 then it follows that //order/@value must have at least one member.


 Cheers
 Rick Jelliffe