next up previous contents
Next: Tree generation Up: System Overview Previous: Blocks

Lexical Redistribution Rules (LRRs)

The third type of machinery available for a grammar developer is the Lexical Redistribution Rule (LRR). An LRR is a pair (rl, rr) of subcategorization frames, which produces a new frame when applied to a subcategorization frame s, by first matching28.2 the left frame rl of r to s, then combining information in rr and s. LRRs are introduced to incorporate the connection between subcategorization frames. For example, most transitive verbs have a frame for active(a subject and an object) and another frame for passive, where the object in the former frame becomes the subject in the latter. An LRR, denoted as passive LRR, is built to produce the passive subcategorization frame from the active one. Similarly, applying dative-shift LRR to the frame with one NP subject and two NP objects will produce a frame with an NP subject and an PP object. Besides the distinct content, LRRs and blocks also differ in several aspects:

ps/lexorg/newelem.eps.gif
{Elementary trees generated from combining blocks

 


next up previous contents
Next: Tree generation Up: System Overview Previous: Blocks
XTAG Project
http://www.cis.upenn.edu/~xtag