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June 8, 2006

Return of Unistroke

Xerox has had a hellacious struggle enforcing 5,596,656, the notorious "unistroke" patent. Xerox targeted 3Com’s “Graffiti”, used in the Palm PDAs. In this episode of a continuing saga, the patent lives to fight another day, as Xerox successfully appeals (CAFC 04-1470), at least partly, an invalidity summary judgment, because of "genuine issues of material fact remaining in dispute."

The ’656 patent discloses a system and method for “computerized interpretation of handwritten text.” ’656 patent, col. 2, ll. 36-37. The system employs an alphabet of “unistroke symbols” that correspond to alphanumeric characters such as Arabic numerals and the letters of the English alphabet. Each unistroke symbol consists of a single, unbroken pen stroke that can be recognized by a computer upon some delimiting operation, such as lifting the pen from a computer-connected, pressure-sensitive writing surface.

In 1997, Xerox brought suit against 3Com Corporation and six other defendants (collectively, “3Com”). Xerox alleged that the ’656 patent was infringed by 3Com’s “Graffiti” system for handwriting recognition, which is used with 3Com’s PalmPilot handheld digital devices. 3Com then requested that the U.S. Patent and Trademark Office reexamine the ’656 patent. Following consideration of a number of prior art references, including a journal article written by D.J. Burr and a Japanese patent application by Tadahiro Nagayama, the Patent and Trademark Office confirmed the patentability of all 16 of the patent’s claims.

The district court construed the claims and granted summary judgment of noninfringement. On appeal, though generally tracking with the district court on claim construction, the CAFC disagreed on a few claim terms.

In particular, we disagreed with the court’s conclusion that it was clear that the Graffiti symbols were not sufficiently “graphically separated” from each other to be unistroke symbols; that the Graffiti system did not allow for “definitive recognition” of symbols immediately upon pen lift by the user; and that the Graffiti system did not feature “spatial independence.”

The story continues...

On remand, the district court granted summary judgment of infringement. In addition, the court held that the ’656 patent was not invalid because it concluded that this court, in Xerox I, “presumably did not construe the claims in such a way as to be invalid.” Xerox Corp. v. 3Com Corp., 198 F. Supp. 2d 283, 296 (W.D.N.Y. 2001). 3Com appealed from that judgment. On appeal, we affirmed the district court’s claim construction and its grant of summary judgment of infringement. With respect to the issue of invalidity, however, we held that our prior decision on the issue of claim construction “did not obviate the need for a separate validity analysis,” and we therefore reversed the district court on that issue. Xerox Corp v. 3Com Corp., 61 Fed. Appx. 680, 681 (Fed. Cir. 2003) (“Xerox II”).

In doing so, we addressed a point raised on appeal “[i]n an effort to provide some guidance to the district court on remand.” Xerox II, 61 Fed. Appx. at 684... In short, “definitive recognition” occurs when the “system completes the recognition of the unistroke symbol.” Id.

On remand, the district court issued two orders. In its first order, the court granted summary judgment of invalidity. Xerox Corp. v. 3Com Corp., No. 97-CV-6182T, at 16 (W.D.N.Y. May 26, 2004). The court found that “[b]oth the Burr and Nagayama references teach the use of single-stroke symbols that are definitively recognized upon pen lift.” Id. at 10.

Finally, the court held claims 9 and 11 invalid for indefiniteness. Those claims recite an additional limitation that the unistroke symbols must be “well separated from each other in sloppiness space.” The court explained that the claim term “sloppiness space” is ambiguous and “is not clearly defined or explained in the patent to an extent that would allow one skilled in the art to understand how symbols can be well separated in sloppiness space.” Id. at 21. Moreover, the court added that “sloppiness space” is “not a term of art used in the industry, and does not convey a concept that was known in the industry.” Id. at 20. Thus, according to the district court, “there is no way to determine whether or not two symbols do achieve sufficient separation so as to be well separated in sloppiness space.” Id. at 21. Consequently, the court found the term “sloppiness space” to be ambiguous and concluded that claims 9 and 11 are therefore invalid for indefiniteness under 35 U.S.C. § 112. The court further concluded that “[e]ven if claims 9 and 11 are not invalid as indefinite, . . . those claims are anticipated by Burr.” Id. at 21.

And so to the current appeal, with two issues: anticipation, and indefiniteness (claims 9 & 11).


The CAFC reviewed numerous claim limitations, generally finding anticipation by Burr & Nagayama, and thus ruling against Xerox. But the district court's granting of summary judgment seemed hasty, as the meaning of "stroke direction" needed further study.

[A] genuine issue of material fact remains as to whether the Burr and Nagayama references disclose the various “stroke direction” limitations of the asserted claims of the ’656 patent. Because “invalidity by anticipation requires that the four corners of a single, prior art document describe every element of the claimed invention,” Advanced Display Sys., Inc. v. Kent State Univ., 212 F.3d 1272, 1282 (Fed. Cir. 2000), we vacate the district court’s grant of summary judgment of invalidity for anticipation and remand the case to the district court for further proceedings with particular focus on whether Burr or Nagayama discloses the use of stroke direction in distinguishing symbols as that term is used in the patent.

Obviousness in light of Nagayama & Organek for dependent claims 14 & 15 also requires review owing the unresolved "stroke direction" issue.


The CAFC thought the district court a bit sloppy in throwing up its hands on the claimed "sloppiness space." Xerox successfully appealed that the specification was meaningful in defining the term. The standard for finding indefiniteness is quite high.

Addressing the issue of the indefiniteness of dependent claims 9 and 11, the district court concluded that the term “sloppiness space” is ambiguous and is not adequately defined in the patent. The district court observed that “the patent does not explain how one would determine whether or not symbols are sufficiently distinct so as to be well separated in sloppiness space.”

Yet, as Xerox asserts, the specification explicitly defines symbols that are “well separated from each other in sloppiness space” as those distinguished by “substantial angular offset (e.g., at least 45° and preferably 90°) or directional distinction (opposing directions).” See ’656 patent, col. 3, ll. 28-31. The specification also contrasts symbols that are well separated from each other in sloppiness space from the characters of the ordinary Roman alphabets, “which are not reliably distinguishable from each other in the face of rapid or otherwise sloppy writing.” ’656 patent, col. 1, ll. 54-56.

While those descriptions are not rigorously precise, they provide adequate guidance as to the types of symbols that are “well separated from each other in sloppiness space,” particularly in light of the difficulty of articulating a more exact standard for the concept. See In re Marosi, 710 F.2d 799, 803 (Fed. Cir. 1983) (finding claims not indefinite when specification provided “a general guideline and examples sufficient to enable a person of ordinary skill in the art to determine whether” claim limitation is satisfied). Thus, in light of the criteria provided in the specification, we hold that claims 9 and 11 are “subject to construction” and are not “insolubly ambiguous.”

For that reason, those claims are not invalid for indefiniteness. See Bancorp Servs., L.L.C. v. Hartford Life Ins. Co., 359 F.3d 1367, 1371 (Fed. Cir. 2004) (holding that a claim will not be held invalid if the “meaning of the claim is discernible, even though the task may be formidable and the conclusion may be one over which reasonable persons will disagree”). We therefore reverse the district court’s grant of summary judgment that claims 9 and 11 are invalid for indefiniteness.

Anticipation Over Indefiniteness

The CAFC caught out the district court for sloppiness in finding anticipating on top of indefiniteness, vacating that portion of the ruling.

In the alternative, the district court found that “[e]ven if claims 9 and 11 are not invalid as indefinite, . . . those claims are anticipated by Burr.” The district court explained that “Burr teaches the use of symbols that are well defined in terms of sloppiness space.” The court, however, did not explain how it interpreted the term “sloppiness space.” To be sure, that is not surprising, considering that the court in its indefiniteness ruling had just found that term insolubly ambiguous. As a consequence, however, the district court’s analysis provides little insight into how Burr discloses the limitation of sloppiness separation, other than to suggest that if the Graffiti symbols are well separated in sloppiness space then the Burr symbols must be as well.


And so, another round in upstate New York district court is in the offing.

In summary, while we agree with the district court’s analysis in many respects, we disagree with the court with regard to the “stroke direction” limitation, and we disagree with the court’s indefiniteness and anticipation analysis as applied to claims 9 and 11. Our determination with respect to the stroke direction limitation requires that we vacate the judgment and remand for further consideration of both the anticipation and obviousness rulings. Our determination with respect to the court’s indefiniteness analysis requires that we reverse the judgment that claims 9 and 11 are invalid on that ground.


Posted by Patent Hawk at June 8, 2006 12:10 PM | Claim Construction