COMP9414/9814 Artificial Intelligence

Feedback Quiz on Natural Language Processing - Solutions

Topics: Features and Augmented Grammars; Logical Form

It is best not read the answers until you've tried to answer the questions yourself.

  1. The subcat feature for verbs may take values like none, np, vp:inf, and np_vp:ing. Define each of these and find example of each, either without looking at the lecture notes, or after looking at the lecture notes but giving examples that are different from the ones the lecture notes.

    Answer:
    subcat
    value    		definitionexample
    noneverb can be followed by nothingThe share prices plummeted.
    npverb can be followed by a single npI sold all my shares.
    vp:infverb can be followed by a verb phrase whose verb must be in the infinitive formThe stockbroker decided to jump.
    np_vp:ingverb can be followed by a noun phrase and then a verb phrase with the verb in the present participle formThe reporters photographed the stockbroker plummeting to the ground.

  2. Write an augmented grammar rule for a VP whose head verb subcategorises np_vp:ing.

    Answer: VP → V[np_vp:ing] NP VP[ing]

  3. What can the head subconstituent of a noun phrase be?

    Answer: N - i.e. the head noun, NAME, i.e. the name in a proper noun phrase, or PRO, i.e. the pronoun in a noun phrase that is a single pronoun.

  4. Using the extended chart-parsing technique illustrated in lectures, parse the sentence 1Time2flies3, and show why the ill-formed sentence *1Time2fly3 cannot be parsed. Assume grammar rules S → NP VP, VP → V, NP → N, and use the agr feature. Time is an N and fly and flies are Vs.

    Answer: When the word Time is scanned, the constituent
    N1: N(agr(3s)) → "time" from 1 to 2 [using lexicon entry]
    is created. This gives rise to
    NP1: NP(agr(3s)) → N1(agr(3s)) from 1 to 2 [using rule NP → N and constituent N1]
    and hence to the active arc
    ARC1: S(agr(3s)) → NP1(agr(3s)) • VP(agr(3s)) from 1 to 2 [using rule S → NP VP and constituent NP1]
     
    Then either fly or flies is scanned. In the case of flies, we get:
    V1: V(agr(3s)) → "flies" from 2 to 3 [using lexicon entry]
    VP1: VP(agr(3s)) → V1(agr(3s)) from 2 to 3 [using rule VP → V and constituent V1]
    Since

    1. the "from" of VP1 matches the "to" of ARC1,
    2. the first category after the dot in ARC1 is VP, and
    3. the agr of VP1 is the same as the agr of the VP being sought,

    the dot can be advanced in ARC1, to produce a completed arc, and hence the consitituent
    S1: S(agr(3s)) → NP1(agr(3s)) VP1(agr(3s)) from 1 to 3 [using ARC1 and consituent VP1]
     
    In the case of fly, we get:
    V2: V(agr({1s, 2s, 1p, 2p, 3p})) → "fly" from 2 to 3 [using lexicon entry]
    VP2: VP(agr({1s, 2s, 1p, 2p, 3p})) → V2(agr({1s, 2s, 1p, 2p, 3p})) from 2 to 3 [using rule VP → V and constituent V1]
    Since the agr of VP2 does not unify with the agr of the VP being sought in ARC1, in this case the parse cannot be completed.

    Note: In a more complete lexicon, time could also be a verb (as in Let's time how long it takes) and fly and flies could also be nouns. Of course, there would also be more grammar rules in a more complete grammar!

  5. What are the components of the logical form language described in lectures?

    Answer: terms, predicates, propositions, quantifiers, predicate operators, modal operators, tense operators, term constructors.

  6. From what sentence might the following logical form come?
    eat1(E2,agent[name(M2, 'Mary')],
      theme[the(P1, pizza1>)],
      at-loc[a(R1, restaurant1>)])

    Answer: Mary eats the pizza at a restaurant.

  7. What is a speech act?

    Answer: A speech act is the effect or intended meaning of a sentence. It can differ from the literal meaning. If someone says "Joe Nasty murdered his mother", then depending on the circumstances, this could be an accusation, or providing information, or an expression of horror, or disbelief, or ...

  8. Write down the logical form for Who gave you the flu?

    Answer:
    wh_query(past(give1)(E1, agent[wh(W1, person1)],
      theme[the<F1, influenza1>],
      recipient[pro(Y1, you1)]))

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