Martin (1992: 326-7):
Separate message parts will be recognised where the grammar itself does the work of constructing elaborations. The following relational clause types will thus be interpreted as instantially connecting two message parts:
RELATIONAL: ATTRIBUTIVE:CLASSIFYING/INTENSIVE[5:32] Ben is a sprinter.[4:2:7.n.] That's [[because it's a low dog]],
RELATIONAL: ATTRIBUTIVE:COMPOSITION/POSSESSIVE[5:33] The court has lines.
 Composition and possession are types of extension, not elaboration. The three types of relation in relational clause systems, intensive, possessive and circumstantial, correspond to the three types of expansion: elaboration, extension and enhancement, respectively.
 Hasan's notion of instantial lexical cohesion — equivalence, naming and semblance — refers to 'cohesive devices that are entirely specific to a single text' as opposed to the general devices that are 'a general fact of English' (Hasan 1985: 81-2). The meronymic relation between court and lines is thus general, not instantial.