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Re: What class of grammars is an XPath?

• From: Michael Kay <mike@saxonica.com>
• To: xml-dev@lists.xml.org
• Date: Thu, 27 Jan 2011 09:36:54 +0000

>
> Anyway, it is an interesting question. I think the same question could 
> be asked, rephrased, as "what is the smallest class of formal grammars 
> that every Xpath (evaluating to boolean) belongs to?"
>

I don't understand the question. There's no grammar that precisely 
describes the set of documents for which the expression

sum(//order/@value) > 826

returns true. It's not a grammatical constraint.

Michael Kay
Saxonica

• 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>