In the last issue of Information Flow, I explain faceted classification or access systems.  Essentially they are about allowing users to access content (whether by search or by navigation) from whatever angle they are thinking about it.

Our VP of marketing at Inxight David Spenhoff, who worked at an ecommerce catalog company in the past, commented that this seems to be like "parametric search," which is the dominant catalog search model especially in complex product environments such as electronic components.  Yes, indeed, parametric search is about searching for objects by any of their attributes.  Indeed it's just like a structured query on a relational table, anyway, another angle on the "relational" analogy of Marcia Bates.

The challenge arises in defining or conceptualizing facets for content collections that effectively anticipate how users might want to come at the content.  It's a lot easier for Wines, Cheese, electronic components, and so on, especially when the stuff is already stored in databases and regularly thought about in standard ways.