Online catalogs have been in existence for several years now, but they are still in their infancy as compared to other aspects of library automation and librarianship. Today's best online catalogs are more powerful, more flexible and easier to approach than were most early examples; tomorrow's best online catalogs should be better than today's. Two characteristics have always been true of online catalogs and will always be true: first, that there will be several distinctly different good designs; second, that every good design will reflect conscious choices among different desirable features, some of those choices involving compromises.published or submitted for publicatio