parameters for actions?

When I started looking at actions in SWIXML, I was thinking that the
specified action would be a method and the syntax of the XML would allow
for specifying parameters to that method.  

It appears that the specified action is always a class, not a method
(please correct me if I'm wrong).  If this is true, how can I specify
what parameters this action should look for when it responds to it's
associated event? Does the action class need to be written in a way
where it is expecting to find certain values of widgets through the
component hierarchy?  The examples seem to perform very basic actions,
and don't use any parameters or components in their methods, so they are
not helping me very much. 


I don't want to get into comparing XMLGUI frameworks, but since I see
occasional references to Thinlet which gives me the impression that many
on this forum are also familiar with Thinlet, I want to use Thinlet as
an example.  In Thinlet, it appears that actions are tied to methods,
and you can specify parameters for those methods.  I guess this was more
of what I was expecting to see when looking at SWIXML. 

Any information on this subject will help me alot!  Thanks.