Abstract flow diagrams?

Hi,

would anyone be aware of an XSL and/or SVG based "diagramming" tool that

would read an abstract xml description of the (diagram) model, and
generate a 
visual representation of it. I am at the moment thinking of flow
diagrams, but the
concept should apply to any kind of diagramming model.

The concepts for flow diagrams are quite limited: data, condtions,
actions, ...
Is there a human-friendly xml vocabularly to express a flow using these
concepts
(that could also be edited manually!) ? 
And, would there be any existing XSLTs to render (and add all
non-logical info) this 
in SVG or some other visual format?

I am aware of XMI (XML Metadata Interchange Standard) that may do this,
but
it seems horribly heavy. 

Appreciate any pointers.

Many thanks, mario


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