6.4 Breadcrumbs and Bookmarks

Breadcrumb navigation aids have also been suggested by Mark Bernstein [Ber88]. They provide a visual indicator that a particular node has already been visited. The concept is inspired by the fairy tale of Hansel and Gretel, where Hansel marked their way in the dark forest by throwing breadcrumbs on the floor every few inches. Eventually, breadcrumbs accumulate to a point where they are marking most of the nodes, at this point their utility is minimal. Bernstein suggests that breadcrumbs disappear after a certain time. "...Crumbs represent pages we have read recently, and imaginary birds remove breadcrumbs the reader leaves unvisited for more than thirty pages..."[Ber88,p 43].

The breadcrumb feature has been implemented in WWW browsers such as Netscape by coloring links to pages that have already been visited. The user can specify an expiration time to the coloring, after the time has expired, the links are reset to their original color.

Bookmarks are similar to breadcrumbs in that they mark places that the user has visited. They are much stronger than breadcrumbs in that book marks are permanently stored for later access. The book mark feature has been readily adapted from the printed book, and has proven invaluable for keeping track of places useful to the reader (see figure I.14 for Netscape's implementation of book marks).