clipPath and silhouette

Hello,

I need some clarification on clipPath. In the spec, I can read:

"The silhouettes of the child elements are logically OR'd together to create a 
single silhouette which is then used to restrict the region onto which paint 
can be applied."

My question is : what's the silhouette. 

As an example, I have a shape with stroke and filter. The silhouette is:

a. the shape (without considering any style attribute)
b. the stroked shape without the filter and the "heavy" style attributes
c. the outline of the stroked, filtered... shape


Any comments?
Thierry.

-- 
Thierry Kormann
email: Thierry.Kormann@sophia.inria.fr  http://www.inria.fr/koala/tkormann/
Koala/Dyade/Bull @ INRIA - Sophia Antipolis