Just remember this: the agent of a sentence is the one doing the action of the verb. Consider the following sentences:
(1) The car struck the fence.
(2) The fence was struck by the car.
In both (1) and (2) it is the car that is doing striking, even though in (2) it is NOT the subject. It is the subject that does the action of the active sentence, and the noun of the prepositional phrase in the passive (if the sentence has a prepositional phrase at all) that is the agent.
While the seven sentence pattern description is the norm in English linguistics today there still persists the use of five sentence description in some non-English speaking countries like Japan which teach English as a foreign language.
Essentially the seven sentence pattern is a five sentence pattern with the extra two pattern as extensions of SVA and SVOA. The problem is that some common sentence patterns seemingly cannot be described by the five sentence pattern model. Take sentence (1.), for example:
- John sat up.
There is ‘John’ and he is performing the action of sitting up from perhaps a slouched position. In other words there is one actor doing one action. Therefore it is an SV pattern (John (S) / sat up (V)). Now consider (2.):