The German appeal court has overturned a decision by the German Federal Patent Tribunal to declare Microsoft's patent for the File Allocation Table (FAT) file system invalid. In judgement number X ZR 27/07, handed down on Tuesday, the tenth civil division of the Karlsruhe-based court confirmed the enforceability of the company's commercial rights in Germany. It has not yet published its reasoning, but has confirmed the decision in a short press release (German language link).

The case revolves around patent rights for a "common namespace for long and short file names" conferred by European Patent Office patent number EP 0618540, which is based on US patent number 5,758,352. The common namespace solved the problem of short file names made up of a maximum of 8 characters encountered in older operating systems such as MS_DOS. The company applied for patent protection for the process of linking a second directory entry to the short file name allowing two-way access to the corresponding information.

In 2007, the German Federal Patent Tribunal declared that the invention had no right to protection under European law, as it was not the result of an inventive step. The court found that the patented method had in particular already been suggested by specifications for the Rock Ridge Interchange Protocol (RRIP) for reading files on CD-ROMs, the first version of which dates from 24th July 1991. The group behind the protocol took it upon themselves to extend the ISO 9660 standard for directory entries so that it would also be possible to access CD-ROM content using POSIX file system semantics. This, according to the court, involved determining the location in which a file is stored using the process described in the Microsoft patent.

The German appeal court has now stated that it is unable to understand the lower court's interpretation. It takes a different view of the patent's meaning. It notes that the method of the patent enabled Microsoft to introduce the VFAT file system (in Windows 95), which allows long file names, but remains compatible with the original FAT file system. This solution is, according to the court, made possible by using the file attribute field when storing a long file name, causing the name entry to be ignored when processing data using this system.

According to the court, the method of the patent is to store two independent directory entries, one with a short name and one with a long name. By contrast, in RRIP "both names are contained in the same directory entry". The patent's inventor would have faced "other problems in overcoming" the eight character file name limit. The appeal court's decision brings it into line with the US patent office's assessment of the FAT patent. In early 2006, after lengthy deliberations, the latter confirmed the rights to protection conferred by patent number 5,579,517, claiming that the development was new and inventive.

Appeal court judgement X ZB 22/07 (german language link) of 20th January 2009 had previously reaffirmed the impression gained by critics of software patents that young judges at the Karlsruhe-based appeals court considered it a progressive move to fit in with European Patent Office case law and to interpret the non-patentability of computer programs "as such" accordingly. In a practice which has proved highly controversial, the EPO has long granted patents for "computer-implemented inventions". Last year a German appeal court judgement concerned patent rights for a "control system for investigative modalities"; The judges found that the key issue for whether a patent should be granted was "whether the method seen as a whole serves to solve a specific technical problem which goes beyond data processing."

(Stefan Krempl)

(Stefan Krempl / djwm)