Generating grammars

We have used our tool to specify a grammar for English in order to produce the trees used in the current English XTAG grammar. We have also used our tool to generate a large grammar for Chinese. In designing these grammars, we have tried to specify the grammars to reflect the similarities and the differences between the languages. The major features of our specification of these two grammars^26.3 are summarized in Table and .

 

Table: Major features of English and Chinese grammars

	English	Chinese
examples	passive	bei-construction
of LRRs	dative-shift	object fronting
	ergative	ba-construction
examples	wh-question	topicalization
of transformation	relativization	relativization
blocks	declarative	argument-drop
# LRRs	6	12
# subcat blocks	34	24
# trans blocks	8	15
# subcat frames	43	23
# trees generated	638	280

 

 

Table: Comparison of the two grammars

	both grammars	English	Chinese
	causative	long passive	VO-inversion
LRRs	short passive	ergative	ba-const
		dative-shift
	topicalization
trans blocks	relativization	gerund	argument-drop
	declarative
	NP/S subject		zero-subject
subcat blocks	S/NP/PP object	PL object	preverbal object
	V predicate	prep predicate

 

By focusing on the specification of individual grammatical information, we have been able to generate nearly all of the trees from the tree families used in the current English grammar developed at Penn^26.4. Our approach, has also exposed certain gaps in the Penn grammar. We are encouraged with the utility of our tool and the ease with which this large-scale grammar was developed. We are currently working on expanding the contents of subcategorization frame to include trees for other categories of words. For example, a frame which has no specifier and one NP complement and whose predicate is a preposition will correspond to PP P NP tree. We'll also introduce a modifier field and semantic features, so that the head features will propagate from modifiee to modified node, while non-head features from the predicate as the head of the modifier will be passed to the modified node.