Martin (1992: 323):
The concessive relation in [5:30] below for example marks the fact that Becker's double faulting was unexpected in the field. In this way it is concessive relations, rather than temporal or consequential ones that provide the main textual evidence for the presence of expectancy relations between activities in activity sequences deriving from a given field.
[5:30] Becker served for the match in the third setbut double faulted three timesto level the set.
 In SFL theory, the logico-semantic relation in the first clause nexus is variation: replacive (a type of extension), not concessive (a type of enhancement), because the meaning realised by the wording is 'not X but Y', not 'if P then contrary to expectation Q'.
 The field that this text realises is tennis reportage. 'Expectancy relations' feature in the semantics, not in the field — in the language, not in the context.
 In SFL theory, these 'activity sequences' are ideational meanings which realise a context whose field is tennis reportage. They are the content of language, not the context of language.