converting Sybase RULE -> postgreSQL

Hi,

I am still a novice at this so bear with me.
I am going to try to alter a Sybase TABLE create script (excerpt
below)to postgreSQL.

I suspect some of the script is specific to Sybase and I'll just need to
remove it. In particular there are numerous stored procedures ("sp_").
But first things first.

RULES:

In the sample below the RULE CloneEnd_type restricts input: the only
data which can be inserted or updated into CloneEnd.type have to be one
of 'BAC_end', 'YAC_end' etc..

I know postgresql supports RULES but have not used them prior. How would
one cone this for postgresql?

Stored Procedures:

Are FUNCTIONS (postgresql)equivalent to stored procedures (Sybase)?

### Sybase code: ###

CREATE RULE CloneEnd_type_rule
AS @col IN ('BAC_end', 'YAC_end', 'TAC_end', 'EST', 'unknown', 'P1_end', 'plasmid')
go

ALTER TABLE CloneEnd
ADD PRIMARY KEY (clone_end_id)
go

exec sp_primarykey CloneEnd,
clone_end_id
go

exec sp_bindrule CloneEnd_type_rule, 'CloneEnd.type'
exec sp_bindefault Set_To_Current_Date, 'CloneEnd.date_last_modified'
exec sp_bindefault Set_to_False, 'CloneEnd.is_obsolete'
go

regards,

Charles