The U.S. Patent and Trademark Office will allow the Microsoft Corporation to make a case that it is not infringing a patent owned by the University of California.

The case revolves around browser plug-in technology that was developed by Michael D. Doyle in 1993, while he was a researcher at the University of California at San Francisco. The university was granted a patent for the technology in 1998 and licensed it exclusively to Eolas Technologies, which is owned by Mr. Doyle.

The university sued Microsoft for infringement in 1999, and victories in the case have gone back and forth ever since. In 2003 a jury ordered Microsoft to pay more than $520-million to the university, but an appellate court partially overturned that verdict. Meanwhile, the patent office has gone back and forth on the patent’s standing. In a preliminary ruling in 2004 it declared the patent invalid. But in 2005 the office reversed that ruling.

Last week the patent office agreed to revisit the question of who first invented the technology in question. Officials at Microsoft applauded the most recent development. Microsoft has maintained that it was the original inventor of the technology. —Scott Carlson