I realize this is completely pretentious, and I humbly ask forgiveness from the great Ranganathan, but....
The Five Laws of *Library Catalogs* for the 21st Century1. The catalog must be relevant to the needs of its patrons.
2. The catalog must change as the needs of its patrons change.
3. As much as possible, the catalog must help its patrons understand what information is *really* available to them, not only what is held within the local collection.
4. If patrons do not come to the catalog, the catalog must go to the patrons.
5. The catalog must include the knowledge and information of non-librarians.
Five Laws of *Library Catalog Records* for the 21st Century1. Catalog records must be created and maintained efficiently.
2. Catalog records must reuse relevant data input by other agencies.
3. Catalog records must work coherently (i.e. interoperate) with catalog records created by other cataloging agencies.
4. As much as possible, catalog records must work with resources made for non-library purposes.
5. Catalog records must be made freely available for use by other developers in the world.