one-of and other questions on goo's type system

Hello folks,

I just tried out goo and I must admit I like it :-).  Below are some 
problems and questions I encountered:

First of all I'm missing something like Dylan's one-of function aka:
(df one-of (args|...) (app t+ (map t= args)))
I think it's a reasonable common function to be included.  But maybe I just 
overlooked it.

Which unfortunately happens rather easily as the naming convention seems to 
be use 2 or 3 characters 4 at the most
:-).  Well maybe I just need some more time to become used to it. (I 
recently programmed a lot in Eiffel credo:
keystrokes are cheap).

Is there a formal type conformance definition?  Especially considering t=, 
t?, t+ and t* .

How can I declare a class to be abstract?  Is there a tool or at least 
convention to write selfdocumenting libraries.  In the style of ocamldoc 
javadoc ...?


Cheers,

Bene