Faceted Browsing

What is faceted browsing?
"Unlike a simple hierarchical scheme, faceted classification gives the users the ability to find items based on more than one dimension. This is becoming a popular and useful way to narrow large results sets and make the different types of metadata more easily seen and used." (from here)

My interest in all of this in to see if some form of faceted browsing could be used as a discovery tool for astronomical databased, more precisely for astronomical metadata databases.
I am clearly thinking about Virtual Observatory registries and the potential for discovery. However, the current state of the registry metadata is simple not adequate for coherent discovery and I am interested in looking in self-organizing and self-metatagging software that will allow the creation of a new type of astronomical registry where faceted browsing might indeed be a valuable alternative to simple searching.

Of interest are some applications of faceted browsing I have recently found:
Images: Flickr Related Tag Browser
Extended Searches: Sputtr, Symbaloo, Tafiti (based on MS Silverlight)