A patent application exists for the technology behind the workings of the iPod and its user interface (UI) that may explain HP's decision to license the product, and why other MP3 players can't match its ease of use, according to an attorney.

Writing for Mac Observer, US attorney John Kheit reveals that Apple filed a patent application for a "Graphical user interface and methods of use thereof in a multimedia player", on October 28, 2002. This patent application was published by the United States Patent and Trademark Office on March 25, 2003.

Kheit suggests: "Considering that one of the major distinguishing features of the iPod is that it is simply way easier to use and navigate; having a patent on the interface presents a big obstacle to knock-off artists. Dell and other would-be pretenders to the MP3 throne will actually have to come up with their own UI or license it from Apple. This makes HP's decision just to outright license the iPod a lot more understandable."

He adds: "So far, the competition has managed to match or best Apple's MP3 designs in every aspect except ease-of-use. In price, in extra features (hello – what's it going to take for Apple to put an FM radio in an iPod), in battery life, and even size and capacity, other MP3 makers have bettered the iPod.

"However, the UI on other players just plain sucks. Beyond Apple balancing the feature set of the iPod and making it look attractive to most people, the iPod's greatest market differentiating feature has been ease of use."

Kheit asks: "The question is can or will someone else come up with a navigation UI that is "good enough" without getting sued by Apple?"

If the patent application is approved, "it may turn out to be a big ace-in-the-hole for Apple".

"Had Apple secured patents on its desktop user interface, many years ago, the entire landscape of the computer industry would likely be very different today," Kheit observes.

The patent application describes a: "Graphical user interface and methods of use thereof in a portable multimedia device, a method, apparatus, and system for providing user supplied configuration data. In one embodiment, a hierarchically ordered graphical user interface.

"A first order, or home, interface provides a highest order of user-selectable items each of which, when selected, results in an automatic transition to a lower order user interface associated with the selected item. In one of the described embodiments, the lower-order interface includes other user selectable items associated with the previously selected item from the higher order user interface."

The inventors are listed as Jeffrey Robbin, Steve Jobs, and Timothy Wasko.