This is probably the most interesting case (Microsoft vs PartsRiver) and sheds the most light I think on what is going on:
http://docs.justia.com/cases/federal/district-courts/califor...
"A patent is invalid pursuant to 35 U.S.C. § 102(b) if the
claimed invention is offered for sale more than one year before the filing date of the patent application. Here, the "critical date" is October 14, 1993, which is one year before the filing date of the ‘821 patent application.
The Court concludes that claims 1 and 2 of the ‘821 patent are invalid due to the on-sale bar because they were the subject of a commercial offer for sale of an invention that was reduced to practice before October 14, 1993."
This was were the initial patent was ruled invalid due to the OnSale bar. Not being a lawyer, I'm not sure how changes they made to it made the OnSale bar no longer valid. Do the changes somehow effect the patent/conception date?
The original filing date was October 14, 1994 and, according to the above court documents:
"As noted above, Danish, a co-inventor of the ‘821 patent, and Plaintiff have conceded that claims 1 and 2 were reduced to practice in April, 1992"
It is tough to claim prior-art as early as '92 or '94. But, if the changes to the patent somehow makes the onsale bar no longer valid, does it change or negate those two dates.
Prior-Art could be claimed on a few different things. Faceted search can definitely be found in different things as early as the late 90s:
http://idl.ils.unc.edu/rave/history.html
http://en.wikipedia.org/wiki/Faceted_search
It might be a stretch but, as others have stated, you could make an argument that faceted search has prior-art as early as the mid 1930s:
http://en.wikipedia.org/wiki/Colon_classification
There are a few libraries that use it but it isn't clear when it was instituted.