Re: System properties

>>>>> "Mike" == Mike Brown <[email protected]> writes:

    Mike> I think that it is the processor's prerogative as to whether
    Mike> to expose such modifications. I would guess that most
    Mike> implementers would not want to bother keeping track of the
    Mike> original state of the environment, but I suppose that leads
    Mike> to another question: should this be side-effect free?

Of course a call to system-property MUST be side-effect free.
That is - to XSLT - if the processor wants to make a copy of the
environment for this purpose (and I guess that's what your next
paragraph is implying), then this is not a side-effect that will be
visible from within XSLT, and so does not concern us. (It might
concern the implementor though, and (s)he might want to document that.)

    Mike> If so, then environment variables should be exposed the same
    Mike> way through the entire transformation.

Yuck!
As long as you are only requiring that a given environment variable
will always have the same value (as seen by system-property)
throughout the transformation, then I'm happy enough.
But if you are requiring coherence for the set of environment
variables as a whole (as seen by a nasty, nosey, snooping external
program), then I'm not so happy. But I guess you didn't mean that
anyway, nor is it likely that such an incoherency would happen in
practice (unless some nasty impure extension function were to modify
the environment - in which case the author of such nasty extension
function can be blamed). . 

So to put it formally:

The result of a call to system-function (exslt-env:X) shall always
return the same value (for a given X) throughout the transaction.

then +1.

    Mike> +1 overall.

    Mike> I would add:

    Mike> Some operating systems store environment variables as
    Mike> encoded text, without any information about what encoding
    Mike> was used. The mapping of such data to an XPath string object
    Mike> is implementation-dependent.

Good point.
+1
-- 
Colin Paul Adams
Preston Lancashire