Object-relational features

Hello,
For my object-relational database class I decided to use PostgreSQL
because it is my favorite database and it calls it self a ORDBMS.  Little
did I know that it supports supports very little OR features.  For
example, using "create type as" is totally worthless because you can't use
it as a field type in a table; you can't compose in another "create type
as"; and you can't inherit another composite type.  The only way to create
a true type is to use "create type" and write C code as a shared object,
so I'm basically doing everything C, which is not something I want to do.
I've searched the mailing lists and have found little said about the OR
features.  Am I missing something here?  Does PostgreSQL support OR
features similar to Oracle 9i (which is what I'm forced to use).  I really
do not want to use Oracle because I have to switch over to my Windows
partition, and Oracle takes about 100 MB of virtual memory on my 256 MB
machine.
Thanks,
Yasir