Re: [xml-dev] What class of grammars is an XPath?

> 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.

Michael Kay
Saxonica