369: add fixed-prefixes attribute in XSLT - #470

I'm not a fan, really, but I won't stand in the way.

Do I understand correctly that if I say fixed-prefixes="local" in an imported stylesheet, the binding varies depending on who imports it? What happens if it has its own xmlns:local declaration? What happens if it's used as a top-level stylesheet?

Do I understand correctly that if I say fixed-prefixes="local" in an imported stylesheet, the binding varies depending on who imports it? What happens if it has its own xmlns:local declaration? What happens if it's used as a top-level stylesheet?

If it has its own xmlns:local="xxxx", that takes precedence. Otherwise, yes, it depends on who imports it. Which is a little bit scary (though not unlike chameleon schema documents in XSD). But I think it's viable, and it certainly makes it a lot easier to maintain consistent namespace declarations across a large multi-module stylesheet. I found this was a lot easier to specify than the idea of importing namespace definitions from some common shared place, and I think it's easier to use because you just declare the namespaces in your top level module and let them cascade down.

It's not an intended feature that you can load the same module and bind it to different namespaces on different occasions, but I guess people might find some smart ways to exploit that. Which might or might not be desirable.

If the module is used at the top level, you'll get a static error saying "local" is undefined.

I have submitted a substantial revision of the proposal to take comments into account (particularly from @dnovatchev). Namespaces are no longer automatically inherited from including/importing modules, though this can be achieved if required by using shadow attributes and static variables. Namespaces may now be adopted from an external XML document, which can be any document at all, including but not confined to a stylesheet module or a specimen source document.

The CG agreed to merge this PR at meeting 056.