Oid and Oid Vector

Hi!

I'd like to know why the field Oid can't be used as a foreign key. And
more information about the type oidvector. What is
it??????????????????? I can't find information about it anywhere.

I'm asking these questions because i wanted to use the oid field as
primary key of may tables, and relate them using the oid too. I i
wanted to use the oidvector for this kind of things too.

help! 

Thankx, 

Camila
Goiania/GO/Brazil