IDL syntax

Hi,

I'm sitting down to write a *simple* IDL compiler and looking for
suggestions on "user friendly" syntax -- subject, of course, to
precision/accuracy.  (i.e., I can come up with nice clean syntax
that ends up *ambiguous*!)

I'm targeting C/C++ bindings.

The first question is whether I should allow the IDL specifications
to act *as* the "formal" interface specifications for those language
bindings (i.e., include them *directly*) or if I should require the
compiler to run and generate suitable headers which are *then* included?

Also looking for ideas as to syntax for in, out, in/out specifications
on parameters -- without unnecessarily cluttering the sources (and the
IDL specs).  E.g., be pedantic and require EVERY parameter to thusly
be indicated?  Or, just the "unexpected" ones (e.g., outs)?

As this adds an extra layer of complexity to the interfaces, I'm
hoping to make the syntax intuitive (least surprise).

Thx!