Postgres object orientation

Hi.
Some questions on object-orientation of Postgress:
Firstly, is there any possibility of using directly a class name as a type for
another class attribute, without using an explicit key linking, as in a full
ODBMS ?
For example :
CREATE writers(name TEXT)
CREATE books(authors writers[])
Secondly, how does inheritance affect auto-generated primary keys ? Is it
unique among all inherited classes ?
For example :
CREATE cities(id SERIAL, name TEXT)
CREATE capitol INHERIT cities(country TEXT)
Can i be sure that there won't be two identical id in thoses two classes, and
that a SELECT name FROM cities* WHERE id=x won't return two names ?
Thanks for your help.
Subsidiary question : why is mySQL excluded from RDBMS comparison on postgress
www site ?

--
Guillaume Rousse
*******************************************
Iremia - Universit de la Runion
15 avenue Ren Cassin, BP 7151
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Mail:Guillaume(dot)Rousse(at)univ-reunion(dot)fr

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