Parameterized Types and Session Memory

Questions:

a)  Parameterized Types

I was wondering if a parameter mechanism is/will be
available in 4.5 for user defined types.  Currently,
VARCHAR(10), NUMBER(6,2) are parameterized types, 
this is more or less what I'm after (only it'd be
great if strings could be parameters too)

Why?  I'm creating types from abstract algebra
(group theory) and there are an infinite number 
of them, thus I need several parameters to specify 
the information.  

Even if it allowed one integer, this would be cool,
since I could load a table with the options, and
then pass the OID of the tuple.

b) Session Memory

I was wondering how I can get to memory area associated
with a user's session, similar to the package level 
variables in Oracle.

Thanks!

Clark