Prepositions

Case is assigned in the XTAG English grammar by two lexical categories - verbs and prepositions.^4.3 Prepositions assign accusative case (acc) through their <assign-case> feature, which is linked directly to the <case> feature of their objects. Figure 4.4(a) shows a lexicalized preposition tree, while Figure 4.4(b) shows the same tree with the NP tree from Figure 4.3(a) substituted into the NP position. Figure 4.4(c) is the tree in Figure 4.4(b) after unification has taken place. Note that the case ambiguity of books has been resolved to accusative case.

  

Figure 4.4: Assigning case in prepositional phrases

(a)		(b)		(c)