Microsoft may not be able to challenge the iPod's success in the marketplace, but in the marketplace of ideas - or, at least, patents - it has succeeded in challenging Apple's attempt to patent a piece of the digital music technology, reports CNET. Apparently, a patent examiner last month rejected Apple's application to patent some iPod user interface concepts because a Microsoft developer had filed similar claims several months before Apple. A Microsoft rep cheekily noted on Friday that the company is open to licensing its technology.

Although the patent decision is considered "final," Apple can try to redefine the scope of its patent so it does not overlap with Microsoft's patent application. In a statement, Apple said it "invented and publicly released the iPod interface before the Microsoft patent application cited by the examiner was filed." It also said it "has received many patents for inventions related to iPod, and has many more patents pending."

"The U.S. patent process is often a lengthy one, involving much back and forth with the U.S. patent office," Apple also said. "Apple will continue to pursue this patent application, as well as the many others covering iPod innovations."

BusinessWeek reports that Microsoft's patent application for "auto playlist generation with multiple seed songs" concerns ways that a device can learn from a user's behavior - in this case, repeated selection of music - to populate a music playlist.

Such "machine-learning" techniques can, for example, be used to develop programs to distinguish spam from wanted email by tracking which messages a user marks as spam. As patterns emerge, the computer can tag spam before the user sees it.