Re: [xml-dev] isXPath1 / isXPath2 -- not(/..)

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

At 2015-12-19 09:49 -0800, Dimitre Novatchev wrote:
> There seems to be something wrong with the type evaluation of Saxon 9.1J
>
> When I evaluate this:
>
>  /.. instance of item()
>
> the result is:
>
>  false()
I think that is correct, because /.. evaluates to the empty set, and 
there are no values in the empty set, so how could the expression be true()?

I get the same with:

  () instance of item()

> As item() is the root of the type system and every possible value is 
> an item(), the above result means that /..  has type that isn't 
> defined anywhere in the type system.
But /.. isn't a value, it is the empty set ... would item() include 
the empty set as a value?

I do get true() with

  () instance of item()?

And if the empty set were a value that is included in item(), then 
one couldn't have a sequence type of "item()?".

I hope this is helpful.

. . . . . . . . . Ken


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