references (foreign keys) and selection lists

Hi,
In my database I have several references between tables.
When webifying an insert form it seemed to me that these
would best be represented as a selection list.

Currently I'm using this:

SQL: select t.tgargs from pg_class c, pg_trigger
where t.tgrelid = c.oid and c.relname='mytable';
returns values like this:
"<unnamed>\000mytable\000myothertable\000UNSPECIFIED\000type\000category\000"
PHP: record = split on '\000';
when record[1] matches mytable:
[If it doesn't match mytable, then this table is being referenced as
opposed to referencing]
SQL: select record[5] from record[2];
PHP: construct selection list from the returned list

Question: Is \000 an official separator between targs fields or is
000 part of a number that may change for some reason?

Also -- is this the best way to solve my problem? It seems a little
inelegant to perform the middle split and match in the calling script, but I
can't figure out how to do it in SQL (tgargs is type bytea which doesn't
respond to regex operators.... What is a bytea anyhow?)

Last question -- Is there any documentation of the system tables (pg_*)?
I've found several useful fields in several tables, but I'm far from
understanding most of what's in there.

Thanks,
Toshio
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