Assignment 5 solution, Ling 645/CMSC 723, Fall 1997

Assignment 5 solution, Ling 645/CMSC 723, Fall 1997



Problem 5.1 [30 points]

;;; Additional lexicon entries
(setq *lexicon-new1*
  '((many       (art (agr 3p)  (root MANY1)))
    (most       (art (agr 3p)  (root MOST1)))
    (admire     (v (root ADMIRE1) (vform bare) (subcat _np)))
    (restaurant (n (root RESTAURANT1) (agr 3s)))
    (Edgar      (name (agr 3s) (root EDGAR1)))
    (in         (prep (root IN1)))))


Problem 5.2 [40 points] ;;; Additional grammar rules (setq *grammar-new1* '((headfeatures (np agr) (vp vform agr)) ;; Rule saying that an NP can be made up of a name. ;; Note that AGR is declared a "head feature" for the grammar that ;; this is being added to, so we don't have to specify ;; explicitly that the agreement features of the NP ;; come from the agreement features of the name; ;; that happens automatically. ((np) -12> (head (name))) ;; Rule VP -> VP PP ;; Note that VFORM and AGR are handled automatically by ;; having those be headfeatures for VP, above. ((vp) -13> (head (vp)) (pp)) ;; Rule PP -> P NP ((pp) -14> (head (prep)) (np))))
Problem 5.3 [20 points] a. Subcategorized PP's are complements to the verb, and the PP in this case is an adjunct or modifier, not an argument. A locative prepositional phrase can apply to practically any verb phrase, but a locative PP argument is only present for certain verbs. b. A number of reasonable attempts could be made using the feature based grammar formalism of Chapter 4, most of them involving the addition of a semantic class feature to the nouns (e.g. adding the feature-value pair (class HUMAN) to the lexical entry of "Edgar") and adding some kind of category constraint as a feature on the argument in a syntactic rule, e.g. modifying the S -> NP VP rule so that the NP's class must match the constraint specified by the verb in the VP. For example: ;; Changes in lexicon: (admire (v (root ADMIRE1) (vform bare) (subcat _np) (subjclass ?human) (objclass ?any))) (bachelor (n (root BACHELOR/SEAL) (class animate) (agr 3s))) (bachelor (n (root BACHELOR/UNMARRIED) (class human) (agr 3s))) (Edgar (name (class HUMAN) (agr 3s) (root EDGAR1))) ;; Changes to headfeatures in grammar *grammar4-5*: (headfeatures (v root subcat subjclass objclass) (n root class)) ;; Changes to headfeatures in grammar *grammar4-7* (headfeatures (s agr) (vp vform agr subjclass objclass) (np agr class)) ;; Changes to rules in grammar *grammar4-7* ((s (inv -)) -1> (np (agr ?a) (class ?c)) (head (vp (vform (? v past pres)) (agr ?a) (subjclass ?c)))) ((vp) -5> (head (v (subcat _np) (objclass ?c))) (np (class ?c))) A problem with this solution is that features are matched exactly -- so, for example, if the subjclass restriction for a verb is ANIMATE and the subject NP has (class HUMAN), the features won't match. An inelegant solution to this problem would be to specify the verb's restriction as a set of possible values, and make sure that whenever ANIMATE is in there, HUMAN is also. This would become unwieldy pretty quickly, though, with any reasonably large set of semantic features.
Problem 5.4 [20 points] a. There are many valid solutions, all of which point out that there must be a feature distinguishing mass/count or some related distinction and also note that "beer" is an ambiguous lexical item, since it can refer to a quantity ("Beer spilled on the table") or a quantized thing ("A beer cost $1.25"). b. "Edgar bought the beer" is ambiguous because the direct object could be either a mass noun (a quantity of beer) or a single bottle of beer.

Return to the course home page.