Martin (1992: 293):
The message part may or may not be realised by a single lexical item; congruent and incongruent realisations are exemplified in Table 5.3.
Table 5.3. Simple and complex lexicalisation of message part MESSAGE PART CONGRUENT(1 lexical item) INCONGRUENT(1+ lexical items) ‘person’ champion tournament winner ‘place’ court playing area ‘thing’ draw playing schedule ‘quality’ outstanding first class ‘action’ smash hit an overhead ‘quality’ well out of sight
 In SFL theory, the distinction between congruent and incongruent realisations is the distinction between non-metaphorical and metaphorical expressions. When the semantics and the lexicogrammar are in agreement (congruent), there is no grammatical metaphor; when the semantics and the lexicogrammar are not in agreement (incongruent), there is grammatical metaphor.
Here the distinction is not used in the SFL sense, but instead used merely to distinguish whether the semantic unit is realised by one word or more.
 There are two layers of confusion here. On the one hand, the elements listed for the discourse semantic unit, the message part, are those that have been previously identified as the field variables that the message part realises. On the other hand, these elements are not field variables, on the SFL model, but semantic elements in a description of social activities.