XML based programming language

[stefaan]

> All of these are grammar-specifications that allow you to define the
> structure of your XML-documents with more constraints.

Ok, I should have foreseen the schema checker answer...my point really
is that
yacc can do even more than just checking the conformance to a grammar.

It also allows me to specify semantic actions,
e.g. to help in building an abstract syntax tree from
the concrete syntax tree, or to implement a very basic
interpreter...

mock example:
<input><definevar name="a" value="10"/><definevar name="b" value="12" /
></input>
<output><sum arg1="a" arg2="b"/></output>

No schema checker can take this specification and simply output "22".
XSLT might be able to implement it, but it is complex for anything
real-life. Elementtree can immediately give me the concrete syntax
tree,
but any semantic actions have to be implemented during a
manually programmed tree traversal.

Anyway, it is not urgent for me, I have something which works,
it just seems like something's missing still from the
existing XML tool collection. Or I am being thick-headed ;)