September 24, 1991 Memorandum to: Members of the X Consortium Subj: U. S. Patent No. 4,555,775 (Pike), Issued to AT&T on November 26, 1985 for "DYNAMIC GENERATION AND OVERLAYING OF GRAPHIC WINDOWS" In February 1991, AT&T sent letters to MIT and to members of the X Consortium, notifying the community that the "backing store" functionality available in the X Window System is an implementation of a patented AT&T invention, and that consequently, companies or institutions commercially marketing or internally developing products based on an X Window System implementation will need a license from AT&T. Since MIT developed the X Window System and distributes it widely, we were deeply concerned by AT&T's action, and we conducted a thorough technical analysis of the patent and similar window system technology. MIT also retained counsel to provide us with an expert legal opinion. Both our technical analysis and the legal opinion conclude that AT&T's claim with respect to the X Window System cannot be sustained. Patent #4,555,775 was applied for in 1982 by Robert Pike and issued in 1985 to his employer, Bell Laboratories. It describes a variation of graphics drawing algorithms that enables a single display screen to support overlapping windows, in which several programs can be active simultaneously. It is our opinion that this same capability was present in window systems that predated the Bell Laboratories' work. The Bell Laboratories' work, the X Window System, and previous window systems all use different variants of the same basic methodology (storing obscured regions of windows as off-screen bit maps). Both our legal and technical analyses agree that each of the patent's claims is either so broad as to have been anticipated by prior art, or so narrow as to apply only to the `775 patent's specific algorithm and not to the X Window System. AT&T has requested the Patent Office to open the `775 patent for reexamination, which will give AT&T an opportunity to clarify the patent's claims. We hope that AT&T will seek there to recognize the contribution of the work on which it is based while not casting its claims beyond the specific methodology involved. MIT is very willing to work with AT&T toward reaching this goal and is exploring ways in which this can be done. From a broader perspective, the confusion over the `775 patent illustrates the difficulties raised by the increasing number of patents issued on software technology. We would welcome the opportunity to join with AT&T, other companies, and the university community to explore ways to alleviate these problems. Software is an area in which prior art is often difficult to identify and in which obviousness differs significantly from one perspective to another. The recent proliferation of software patents is creating pressure on software developers to seek patent protection for straightforward ideas, and increasing pressure to claim broad applicability of software patents, well beyond the scope of any original invention. These practices introduce a chilling effect on university research, and they undermine our ability to pursue ideas in a free and open climate. In as much as these practices attack the university's central goals and its obligation to disseminate information, they are a matter of utmost seriousness to MIT.