  Semantic communication is an emerging research area that has gained a wide
range of attention recently. Despite this growing interest, there remains a
notable absence of a comprehensive and widely-accepted framework for
characterizing semantic communication. This paper introduces a new
conceptualization of semantic communication and formulates two fundamental
problems, which we term language exploitation and language design. Our
contention is that the challenge of language design can be effectively situated
within the broader framework of joint source-channel coding theory, underpinned
by a comprehensive end-to-end distortion metric. To tackle the language
exploitation problem, we put forth three approaches: semantic encoding,
semantic decoding, and a synergistic combination of both in the form of
combined semantic encoding and decoding. Furthermore, we establish the semantic
distortion-cost region as a critical framework for assessing the language
exploitation problem. For each of the three proposed approaches, the achievable
distortion-cost region is characterized. Overall, this paper aims to shed light
on the intricate dynamics of semantic communication, paving the way for a
deeper understanding of this evolving field.
