Horn in Kasher, "Implicature"

In "Toward a New Taxonomy for Pragmatic Inference: Q-
based and R-based Implicature" L R Horn
suggests two principles
(Q and R) which are intended to replace all the maxims of
conversation, except Quality. The Q-principle, hearer-
based, "Say as much as you can (given R)", and the R-
principle, Speaker-based, "Say no more than you must
(given Q)". These principles correspond to two competing
forces identified by Zipf (1949), Speaker's economy:
"(Given m meanings) a vocabulary of one word which will
refer to all the m distinct meanings", and Auditor's
economy: "a vocabulary of m different words with one
distinct meaning for each word".