XSLT in UML

Are there any current efforts or already drafts on the issue of
describing XSLT-templates in a UML-like language? For my thesis I
would like to explain some of the more complex templates using
diagrams. But as it seems there is nothing like UML for the
declarative paradigm, is it?

My inital thought was to use something like a flow-chart as it is used
in procedural languages. Knowing that the diagrams would suggest a
linear execution even though its unknown in which order the
processor calls the templates it seemed like the best approach to me.

Any better ideas? Otherwise I would have to "invent" something myself.
Manuel Baehnisch