Martin (1992: 25):
With ideational semantic relations of this kind, there is no need to propose a discourse Head. Consequently the relationship between expectant items will be modelled with an arrow-less inter-dependency line as outlined below… :As with "hypotactic" semantic structures, these "paratactic" relationships may extend over any number of mutually expectant items to form lexical strings:
Blogger Comments:
[1] To be clear, in SFL Theory, this is lexical cohesion, and its function is textual, not ideational.
[2] To be clear, the notion of 'expectancy' is an addressee-oriented rebranding of collocation, where the cohesive lexical relation is syntagmatic. Here Martin confuses it with hyponymy, where the cohesive lexical relation is paradigmatic; see Halliday & Matthiessen (2014: 644).
[3] To be clear, hyponymic and superordinate relations between lexical items are types of the logico-semantic relation of elaboration, not interdependency. Interdependency is concerned with the equal or unequal status of units in a unit complex.
[4] See the previous post for the problems with these analyses.