A patent for virtual subdomains is being revoked by the US Patent and Trademark office thanks to prior work provided by the Electronic Frontier Foundation. The Office announced its decision today, noting that it rejected all of patent owner Hoshiko's claims since the patent went under examination in 2007.

The patent in question was originally submitted to the USPTO in 1999 by an IP holding company named Ideaflood and somehow managed to get approved in 2004. (The patent eventually got transferred to a new company named Hoshiko.)

Basically, the patent describes virtual subdomains with the idea that it would be impractical for companies with a large number of domains to create new DNS records for each subdomain (like jacquirules.arstechnica.com, for example). The solution would be to use virtual subdomains that put a wildcard in the DNS record—there would only be a single entry, *.domain.com, and it would resolve to a single IP address. The webserver at that IP address would then read the host request and parse it so that it pointed to the specific public HTTP folder residing somewhere on the server.

The Electronic Frontier Foundation took aim at the patent via its Patent Busting Project in 2007, referring to it as a "bogus software patent" that stifled innovation. Together with attorney Rick McLeod, the EFF asked the USPTO to reexamine the patent on the grounds that there was plenty of prior art, including Apache's mod_rewrite module written in 1998 by Ralf Engelschall. Engelschall's work and other people's comments on it were preserved in developer newsgroups and were used to show that this was a commonly understood technology by those "skilled in the art."

The USPTO finally got around to rejecting 20 claims contained within the subdomain patent earlier this year, leaving the folks at Hoshiko to decide whether to amend the claims to make them more narrow. They did, and the claims got rejected once again. "Patent Owner's arguments filed in response of 03/16/2009 have been fully considered but they are not persuasive," the USPTO wrote in its decision. "This action is made final."

Hoshiko can still appeal the decision, but the EFF is happy nonetheless. "This patent was particularly troubling because the company tried to remove the work of open source developers from the public domain and use it to threaten others," EFF Legal Director Cindy Cohn said in a statement. "Ironically, the transparent open source development process gave us the tools to bust the patent!"

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