[xquery-talk] Function for determining one XPath as subset of another

[Pavel Velikhov]

> Well, so, to continue, let's assume that there are no user-defined functions, and in fact the only thing we want to proof is select+filter, where a filter is limited to the default operators. From that is it follows that 
> 
> -path1: select-child-nodes-by-name(select-child-nodes-by-name($context,'x'),'w')
> -path2: select-descendant-nodes-by-name($context,'w')
> 
> And we need to proof that those functions are somehow equivalent. Can it be done?

Its easy to prove that they are not equivalent. You can have nodes with ‘w’ label at multiple levels, including children on $context.