Re: Co-validating stylesheets?

On Thu, 4 Nov 1999, Oren Ben-Kiki wrote:

> XSLT has hit the point where it is "Turing complete" so _in general_ doing
> this validation is impossible. It is possible to write a tool which will
> work most of the time, and complain about specific pieces of the code where
> it can't follow the code. Such a tool would be very useful, since _typical_
> XSLT code would be verifiable.

I certainly think it would be nice to have a tool to say either "given
valid input, this always produces valid output", "given valid input, this
will not always produce valid output", and "I can't tell what will
happen". Perhaps also "given valid input, this will never produce valid
output", but that's probably harder.

What I'm rusty on is the notion of Turing-completeness. I might be
demonstrating my own ignorance here, but I'm wondering if somebody could
provide a simple example of a stylesheet that's just impossible to figure
out whether it co-validates.

> I'm not aware of anyone doing any work along these lines, though.

Nor am I. That's why it's fun :)

Dan


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