I was robbed by a sweet old lady on a motorised cart.
'I' is the subject.
'was robbed' is the verb phrase and 'was' is the operator.
'by a sweet old lady on a motorised cart' is a prepositional phrase.
'sweet old lady' is the agent; what other semantical role(s) does this
noun-phrase play in the sentence? I mean, is it an object or what. No, it is
not, I know, but then, what is it?
'by a sweet old lady' is a prepositional phrase.
'a sweet old lady' is a noun phrase.
'on a motorised cart' is a prep. phrase.
'on a motorised cart' is an adverbial phrase.
Question: Do you agree?