Ex Parte Jung Puts the Conjunctive in the Phrase “at least one of A and B”

August 3, 2018

      Last month, the U.S. Patent & Trademark Office’s Patent Trial and Appeal Board (“PTAB”) newly designated five decisions as informative.  These five decisions included ex parte Jung, a Board decision regarding the construction of the phrase “at least one of A and B.”  According to the Board in Jung, the proper construction for this phrase is the conjunctive, i.e., at least one of A AND at least one of B.  This presumptive construction now applies during patent examination absent certain exceptions.

      Based on its wording, the meaning of the phrase “as least one of A and B” is open to multiple interpretations: a mutually exclusive disjunctive interpretation in which the phrase means A or B; a non-mutually exclusive disjunctive interpretation in which the phrase means A or B or both; and a conjunctive interpretation in which the phrase means A and B.  This ambiguity raises the issue of how examiners should interpret the phrase during examination as the disjunctive interpretations provide a broader construction than the conjunctive one.

      In Jung, claim 1 recited a method for playing back a scene using universal plug and play that included two instances of the phrase “at least one of A and B.”  The first instance recited “at least one of a precedence relation and a connection relation,” and the second instance recited “at least one of a connection branch and a contents connection list.”  Although not expressly construed, the examiner implicitly applied a disjunctive construction of these terms as the prior art only met one element of each instance instead of both.  The applicant asserted the terms required the conjunctive interpretation and appealed to the PTAB.

      The Board in Jung relied primarily on the Federal Circuit’s decision in SuperGuide Corp. v. DirectTV Enterprises Inc., 358 F.3d 870 (Fed. Circ. 2004).  In SuperGuide, the Federal Circuit held that the plain and ordinary meaning for the phrase “at least one of A and B” is the conjunctive interpretation, relying in part on a grammar treatise to support this construction.  Following the guidance of the Federal Circuit, the PTAB also recognized SuperGuide’s exceptions to this construction including express definitions (i.e., being your own lexicographer), a clear disavowal of the conjunctive interpretation (either in the specification or during prosecution), or express and clear support from the specification.

      Despite the specification in Jung having examples consistent with the disjunctive interpretations and, for one of the instances in the claim using the phrase, no example consistent with the conjunctive interpretation, the Board nevertheless held the presumptive interpretation of SuperGuide applied because nothing in the specification expressly disavowed the conjunctive interpretation.  Interestingly, by applying conjunctive interpretation, the Board correspondingly found the claim invalid for lack of written description because the specification provided no example of the conjunctive interpretation.

      To avoid the ambiguity inherent to the phrase “at least one of A and B” and avoid the presumptive conjunctive interpretation if not desired, practitioners have several options available.  If one of the disjunctive interpretations is preferred, the specification can expressly define the phrase as requiring the disjunctive interpretation.  Absent such a definition or other clear disavowal, practitioners would be advised to use different claim language.  For example, practitioners could use alternative phrases such as “at least one of A or B,” “at least one of A and/or B,” or any other phrase whose plain meaning dictates a disjunctive interpretation.  Clarifying the intended interpretation, whether the conjunctive or disjunctive, can also simplify issues during examination and likely shorten examination.  Such clarification can additionally provide benefits should the patent be subject to litigation by short-circuiting any claim construction dispute over the proper interpretation.

Update: on August 7, 2018, the PTAB de-designated this decision as being “informative” because it did not “reflect new or changed policies with respect to claim construction. … The case remains a routine decision of the Board.”

See here.