Re: Function for determining one XPath as subset of a

> even given your easy example
>
>
> 1. //w
>
> 2. /x/y/z/w[@a = 'v']
>
>
> if y is a place holder for an xpath expression rather that just literally
> matching the element y then
> it isn't always a subset, consider
>
> /x/doc('y.xml')/z/w[@a = 'v']
>
> conversely
>
> /x/y/z/w[@a = 'v'] and /x/y[1+1=2]/z/w[@a][upper-case(@a)= 'V']
>
> do select the same sets but to know that you have to be able to prove that
> arbitrarily complicated xpath boolean expressions are true which isn't
> likely to be possible.

Thanks David, I did realise that, I am only looking at simple path
expressions with predicates where the expressions can be determined
statically by only parsing them. So in my instance 'y' would always be
the element named `y`.


-- 
Adam Retter

skype: adam.retter
tweet: adamretter
http://www.adamretter.org.uk