Halliday & Matthiessen (1999: 160-2):
In the simple constructed examples used above, we contrasted doing: happening with pure being; but being also includes 'coming into being', i.e. 'becoming'. In such cases doing and being both construe change leading up to an outcome, but they use different models: Process and Process + Range respectively, For example:
Here the first transition in the state of the lava is represented as doing: happening — Medium/Actor: 'lava' + Process: 'cool'. Coolness is construed as a process; consequently, it is something that is unfolding and which cannot readily be intensified. In contrast, the second transition is construed as being: becoming — Medium/Carrier: 'lava' + Process: 'become' + Range/ Attribute: Very hard*. Coolness is construed as a quality rather than as a process; consequently, it is something which can come into being — which can be attained. The second transition is more closely related to the third: 'it becomes very hard : igneous rock'.However, the two options in construing coolness, as process and as quality, are very close, which is shown by a parallel text associated with an accompanying picture of a volcano:Here the transition in hardness is construed as a process within a figure of doing rather than as a process + quality within a figure of being. Consequently, the hardness is not represented as an intensified "destination" coming into being. Further it can be construed as part of a complex process of cooling-&-hardening within a single figure, as indicated in the analysis above.
