The Problem Of Cracking The Code Of Language As A Semiotic System–&–Process

Halliday & Matthiessen (1999: 510):

There are two aspects to this problem. One is that we do not yet fully understand the nature of a linguistic fact: this is the problem of instantiation. The other is that we do not yet fully understand the relationship that is the semiotic analogue of the “cause : effect” of classical physics: this is the problem of realisation.