Ann,

> It might be easier to define views for normal users that are

restricted to the set of records they can access

this was my first idea, but then I performed some tests that made me
reject it.

1. I built a very simple table:

create table test_table (
field_date timestamp
)

2. I inserted 2 records:

insert into test_table values ('2002-12-29');
insert into test_table values ('2002-12-30');

3. I built a view

create view test_view (field_date) as
select field_date from test_table where field_date>='2002-12-30';

4. I tested the view:

select field_date from test_view

and - as expected - only 1 record was shown ('2002-12-30')

5. I wrote

insert into test_view values ('2002-12-29');

and IT WAS ACCEPTED.

So you see that a view cannot be of much help in my case, as I must
prevent a normal user from inserting dates before a given date.

Thank you

Duilio