In the act of speaking, the speaker adopts for himself a particular speech role, and in so doing assigns to the listener a complementary role which he wishes him to adopt in his turn [...] The speaker is not only doing something himself; he is also requiring something of the listener. Typically, therefore, an ʻactʼ of speaking is something that might more appropriately be called an ʻinteractʼ: it is an exchange, in which giving implies receiving and demanding implies giving in response.
- Halliday (1985), a pag.68