The paper describes "Piles" as an adjunct to the file/folder metaphor, in the paper (co-authored with Richard Mander and Yin Yin Wong). A clue is in the title, which describes piles as a metaphor for "supporting casual organization of information".

Piles were seen as complementary to the folder filing system, which was used more for archiving than grouping recently used, but related documents. "The folder as the sole container type presents an impoverished set of possibilities," the authors noted.

"There are different aspects to Piles," Solomon told us today. "They are a visual representation, but also helping them organize things, as a way to make suggestions. There are fuzzy edges - the computer is presenting you with 'what if?' questions on a pile of stuff.

This would be helped indexing of the contents of documents in real time, much as BeOS' BFS file system indexed metadata attributes in real time using a dedicated system thread. BFS designer Dominic Giampaulo joined Apple last year, and the rumor circuit has consistently suggested that better threading is a priority for the Panther update to MacOS X. Which suggests that Apple has both the will and know-how to provide a system capable of supporting very rich Piles.