Dissecting Sentences

In the final, he may give us a grammar and a sentence and ask us to do a derivation of the sentence in a tree.

Bring the grammar handout with you to the final exam.

• Name an English sentence that the grammar given in class does not generate. "Give me a book." (Any sentence that starts with a verb). You could add S → VP as a rule to make this sentence work. Another sentence would be, "Are you studying for the exam?" Also, "Which books do you like?" It also fails to handle compound sentences (e.g. Mary went to the store and bought an apple.) It won't handle any sentence that starts with a prepositional phrase.

What if we add VP → Verb NP NP? Then we can have sentences like, "Peter gave the children a book."

There's another way to parse besides building trees: sentence diagramming.

A recursive transition network is a nondeterministic finite state automata. But it happens that the nondeterministic finite state automata and the recursive transition network and the CFG generate the same number of sentences.

The Recursive Transition Netowrk diagram is the preffered way to analyze a sentence.

Example: The bird on the roof vanished.

Here, "vanished" is an intransitive verb.

An augmented transition network (ATM) is like a recursive transition network, but it has been augmented with actions. This method of parsing was popular until several years ago when people forgot about it. The idea is that we want to build a subject out of a direct object and indirect object.

"The man ate a pea."

SUBJ (The man)
MV (ate)
DO (a pea)

"The man vanished."

SUBJ (The man)
---- uh oh it won't parse this sentence.

"The apple was eaten by Mary."

Final Register:

  DO (The apple)
  AUX (was)
  MV (eaten)
  Prep (by)
  SUBJ (Mary)

The last step in the trace is abbreviated but the first two steps are accurate:

1. a → b: SUBJ (The apple)
2. b → c…
   S-4: Voice is passive. AUX (was). SUBJ (dummy NP).
3. c → d: MV (eaten), Prep (by), SUBJ (Mary).

Example: The lion was killed by the fire. "By the fire" could mean the lion was killed near the fire or that the fire actually killed the lion. So there will be two parses.