Metadata Protocols

Are there any standard protocols for storing infomation about a database as 'special tables' within that database? For instance, in one of my databases I have a special table for foreign keys:

CREATE TABLE foreign_key
  (
  source_table text NOT NULL,
  source_key text NOT NULL,
  referent text NOT NULL
  );

It currently has 21 entries. The 'referent' attribute is the name of a table which has a primary key of the int attribute 'id'.

Anyway, I wonder if there are some standard ways of doing this sort of thing. The idea is that the same code could perform certain basic operations on a wide array of databases, just by examining the entries in certain special tables.

-- 
Ashley Yakeley, Seattle WA