Halliday & Matthiessen (1999: 162-3):
In the case of elaboration, both 'coming into being' and 'causing to be' can be construed either as forms of doing or as forms of being. However, in the case of extension and enhancement, there is no comparable multiplicity of perspectives: they can only be construed as forms of doing. Table 4(9) sets out the patterns for the three types of expansion.
