Jakobson's work on communications functions appeared in Thomas Sebeok's 1960 book, Style in Language.
Writing about ten years after Claude Shannon, and making no specific reference to his theory of the communication of information, Jakobson's diagrams clearly reflect Shannon's influence. Jakobson distinguished six communication functions, each associated with a dimension or factor of the communication process.
Context was perhaps Jakobson's most important addition to semiotics. Adding context gives us the difference between semantics (the standard dictionary meaning of a word according to the normal "rules" of the language) versus pragmatics, the meaning that may be intended by the sender, or should be inferred by the receiver/interpreter because of the current situation. Jakobson calls this contextual information "denotative," "cognitive," "referential," the "leading task" of a message. Context-dependence alters the "meaning" to suit the purpose of a communication.
Notes:
referential (: the denotative or connotative "aboutness," contextual information, the "third person," someone or something the message is about)
aesthetic/poetic (: information )
emotive (: the addressee's self-expression, attitude, intention, first person)
conative (: vocative or imperative addressing of receiver, second person)
phatic (: no information, checking channel working, are you still there?)
metalingual (: "about" the language itself, checking code working, agreement on the meanings of words)