Halliday & Matthiessen (1999: 252-4):
(II) Sequence ==> Figure
Here the syndrome occurs in a more general environment, that of construing a sequence on the model of a figure — grammatically, the sequence is construed not as a clause complex but as a clause.
They shredded the documents before they departed for the airport ==> (They shredded the documents) before their departure for the airportThey shredded the documents before they departed for the airport ==> Their shredding of the documents preceded their departure for the airport
These examples of a 'sequence ==> figure' metaphor both involved a sequence of the expansion type. However, this type of metaphoric shift also occurs with projection sequences; for example:The colonel declared his innocence.— where the congruent form would be a projection, either hypotactic or paratactic:The colonel declared that he was innocent.The colonel declared, "I am innocent".