Semantic roles of 'direct object'

What are the primary semantic roles of 'direct object'? In particular, I was wondering what the semantic roles of 'direct object' are in such sentences as:

They crossed the river.
He promised her that he would do it.
He did not mention the matter at all.
She left her room.
He would say nothing.
They ate the pie.

Solution 1:

The semantic roles of direct objects are completely dependent on the verbs they are objects of.

When you look at the details, practically every verb with any specificity in meaning (i.e, not a small verb like put, get, or make) has a uniquely limited set of noun types that it can take as object. You can water the plants and the lawn, but not the dog or the children, for instance, though the meaning would be clear.

Indirect objects are almost always receivers (there are verbs like elect with two objects that aren't describing transit, but they're rare), and human receivers at that. But direct objects are, in a sense, part of the verb -- certainly part of the verb phrase -- and the limitations and requirements set by transitive predicates for their direct objects are part of their meaning.

For instance, we have dozens of verbs for talking, including say and tell. Why so many? What's the difference? Lots. Say can take a direct quote, even in a foreign language, but tell can't

• He said "Arma virumque cano" to her.

• She said "I don't speak Latin" to him.

• She told him she didn't speak Latin

• *She told him "I don't speak Latin"

• *She told him "Non loquor Latine"

Tell, but not say, requires an indirect object

• I said to her that it was 5:00.

• I said that it was 5:00.

• I told him what time it was.

• *I told what time it was

... and so on. The details are always different.