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

• From: rjelliffe <rjelliffe@allette.com.au>
• To: Michael Kay <mike@saxonica.com>
• Date: Fri, 28 Jan 2011 16:29:31 +1100

 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

• Follow-Ups:
  • Re: What class of grammars is an XPath?
    • From: Michael Kay <mike@saxonica.com>

• References:
  • Which algorithm do XML Schema validators use to decide if a stringmatches a regular expression?
    • From: "Costello, Roger L." <costello@mitre.org>
  • Re: Which algorithm do XML Schema validators use to decideif a string matches a regular expression?
    • From: Michael Kay <mike@saxonica.com>
  • What class of grammars is an =?UTF-8?Q?XPath=3F?=
    • From: rjelliffe <rjelliffe@allette.com.au>
  • Re: What class of grammars is an XPath?
    • From: Dimitre Novatchev <dnovatchev@gmail.com>
  • Re: What class of grammars is an XPath?
    • From: Michael Kay <mike@saxonica.com>
  • Re: What class of grammars is an =?UTF-8?Q?XPath=3F?=
    • From: rjelliffe <rjelliffe@allette.com.au>
  • Re: What class of grammars is an XPath?
    • From: Michael Kay <mike@saxonica.com>