In July, the U.S. Patent & Trademark Office's Patent
Trial and Appeal Board designated its ex parte Jung decision as
informative (see
here and
here). In this decision, the Board held that the phrase
"at least one of A and B" was presumed to be conjunctive.
That is, the phrase was presumed to mean "at least one of A
and at least one of B."
This holding raised some concern among patent practitioners,
since the phrase "at least one of A and B" often is
intended as shorthand for the Markush phrase "at least one
selected from the group consisting of A and B." The
construction of the phrase "at least one of A and B" as
requiring at least one of A and at least one of B is significantly
narrower than the Markush phrase of "at least one selected
from the group consisting of A and B." The former only allows
for the conjunctive embodiment in which both A and B are present.
In contrast, the latter allows for additional, disjunctive
embodiments, in which (i) A is present but
