Semantics As Interface

Halliday & Matthiessen (2014: 42-3):

Semantics is the highest stratum within language; it serves as an ‘interface’ between language and the environment outside language. This means that semantics interfaces with context, but not only with context — it also interfaces with other systems that operate within context, viz. with the content systems of other semiotic systems and with bio-semiotic systems such as our systems of perception and our system of bodily action (cf. Halliday & Matthiessen, 1999).