(1) A symbolising process is a type of relational process. Halliday & Matthiessen (1999: 599-600):
The ideational resources of language are primarily a theory of experience, so they are reflected fairly directly in consciously designed theories such as those of cognitive science. If we stay within the ideational metafunction, where mental processes are construed, we also find other processes that are complementary to these: those of saying (verbal processes) and symbolising (a type of relational process).
(2) A symbolic process is an alternative name for a verbal process (Halliday & Matthiessen: 2004: 254).
(3) Symbolic processing refers to a projecting figure — interior sensing or exterior saying — that brings another figure into symbolic existence (Halliday & Matthiessen 1999: 129). It involves the symbolic process and the participant engaged in symbolic processing, the Symboliser.
Halliday & Matthiessen (1999: 129):
“Symbolic processing” is a generalisation across sensing and saying that foregrounds the fact that they can both project.
Halliday & Matthiessen (1999: 130):
The interior Symboliser of sensing is construed as a participant engaged in conscious processing.
Halliday & Matthiessen (1999: 153):
The general motif of figures of sensing is ‘conscious processing’; that of figures of saying is ‘symbolic processing’.