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Deep in Microsoft’s TomTom Linux patent claims


What’s what with Microsoft’s patent claims, and a modest suggestion on how to avoid all this patent nonsense now, and in the future: Get the FAT out!

At first glance, Microsoft suing TomTom, the navigation device manufacturer, for patent violations, appeared to be patent business as usual. A closer look at the Microsoft/TomTom lawsuit (PDF Link) showed that three of Microsoft’s eight patents don’t concern navigation systems, but file system usage within TomTom’s Linux-powered devices.

Specifically, Microsoft is claiming that TomTom, and by implication Linux, is in violation of U.S. Patent No. 5,579,517 (“the ’517 patent”l), entitled “Common Name Space for Long and Short Filenames;” U.S. Patent No. 5,758,352 (“the ’352 patent”), entitled “Common Name Space for Long and Short Filenames;” and U.S. Patent No. 6,256,642 (“the ’642 patent”), entitled “Method and System for File System Management Using a Flash-Erasable, Programmable, Read-only Memory.”

While the names of the first two patents are identical, they actually refer to two different aspects of using ‘long’ file names in file systems. In older, 16-bit Microsoft FAT (File Allocation Table) and NTFS (New Technology File System) file systems supported a maximum of 8 characters for the base file name and 3 characters for the file extension. Including the dot separator, this gave 16-bit systems a maximum of 12-characters for a name. With the advent of 32-bit operating systems, the methods in these patents were introduced to ensure backwards compatibility between MS-DOS, early versions of NT, and Windows 2 and 3.x and later Windows operating systems such as Windows 98. The last patent covers a way to handle these file systems on Flash memory.

Long before this case appeared, the PUBPAT (Public Patent Foundation ) tried to get the ‘517 patent, which is the core patent of the trio, overturned. PUBPAT argued that there had been “previously unseen prior art showing the patent, … was obvious and, as such, should have never been granted.” However, in the end, the Foundation was unable to get the U.S. Patent and Trademark Office to overturn the patents (

To astute open-source legal observers, these patents have long been troubling. By requiring vendors to pay a royalty for their use, this could make it impossible for free software systems to read and write to FAT file systems, because their open-source licenses forbid royalty payments.

As Eben Moglen, Columbia University law professor and free software legal expert, points out though, these are still weak patents. “The FAT patents are not the strongest ammo in anyone’s gun. The 517 root patent was successfully examined, but, in my opinion, it’s not strong enough to sue on.”

And, of course, no matter what happens with the FAT patents, there’s always Larry Augustin’s, the open-source venture capitalist, suggestion: Get the FAT out!

Just because we’ve treated FAT as a de facto open standard, doesn’t mean that we need to continue to do so. After all, Augustin observes, we used to use the GIF (Graphics Interchange Format) all the time too, until “Unisys ‘discovered’ a patent that it held on LZW compression that was applicable” to GIF. The result? Almost everyone stopped using GIF. That’s really the best thing we can do with FAT. Once that’s done we can leave these legal battles behind once and for all.