Model Clause 1

Here are some links for model clause, first two are from tahiti.
After i read and understand them, i will share some interesting parts.

http://www.oracle.com/technology/obe/obe10gdb/bidw/sqlmodel/sqlmodel.htm


http://download.oracle.com/docs/cd/B19306_01/server.102/b14223/sqlmodel.htm#sthref1869

http://www.oreillynet.com/pub/a/network/2004/08/10/MODELclause.html