Accessing schema data in information schema

I'm updating the information schema for SQL:2003. I'm having some
difficulties with the "sequences" view. It should look approximately
like this (uninteresting stuff omitted):

CREATE VIEW sequences AS
SELECT CAST(current_database() AS sql_identifier) AS sequence_catalog,
CAST(nc.nspname AS sql_identifier) AS sequence_schema,
CAST(c.relname AS sql_identifier) AS sequence_name,
CAST(null AS cardinal_number) AS maximum_value, -- FIXME
CAST(null AS cardinal_number) AS minimum_value, -- FIXME
CAST(null AS cardinal_number) AS increment, -- FIXME
CAST(null AS character_data) AS cycle_option -- FIXME
FROM pg_namespace nc, pg_class c
WHERE c.relnamespace = nc.oid
AND c.relkind = 's';

How does one get at the missing fields. The only way I know is
selecting from the sequence, but how does one work this into this
query? Somehow it seems that these things should be stored in a real
system catalog.

Ideas (short of using PERFORM in PL/pgSQL)?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/