Halliday & Matthiessen (1999: 160):
Doing and being thus focus on different phases of a quantum of change; but either can be extended in the direction of the other to indicate (with 'being') the source of change or (with 'doing') the outcome of change. When this happens, the wordings that realise a figure of doing and a figure of being may come to resemble one another. For example, take the two wordings he drove his car hot and he drove his friends crazy. They could both be interpreted as Agent + Process + Medium + Range to show them as related to his car drove hot and his friends were crazy respectively. But at the same time they are differentiated as doing versus being: Actor + Process + Goal + Attribute versus Attributor + Process + Carrier + Attribute. This shows that they are related respectively to he drove his car (without the Attribute) and to his friends were crazy (without the Attributor; but not to he drove his friends)', and explains why we get his car drove hot but not his friends drove crazy, and why his car drove hot is agnate with his car ran hot (and his car moved, rolled, travelled) as another kind of happening but his friends were crazy is agnate with his friends seemed crazy as another kind of being.