Here some part of the clause is presupposed from what has gone before — for example, in response to a question. The resulting forms are very varied. Some are indistinguishable from minor clauses, e.g. Yes. No. All right. Of course.; these have no thematic structure, because they presuppose the whole of the preceding clause. Others, which presuppose only part of the preceding clause, have their own thematic structure; the details will depend on which part is presupposed.
Wednesday, 24 May 2017
Halliday & Matthiessen (2014: 127-8):