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 (r_l, r_r) of subcategorization frames, which produces a new frame when applied to a subcategorization frame s, by first matching^26.2 the left frame r_l of r to s, then combining information in r_r 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:

• They have different functionalities: Blocks represent the substructures that are reused in different trees. They are used to reduce the redundancy among trees; LRRs are introduced to incorporate the connections between the closely related subcategorization frames.
• Blocks are strictly additive and can be added in any order. LRRs, on the other hand, produce different results depending on the order they are applied in, and are allowed to be non-additive, i.e., to remove information from the subcategorization frame they are being applied to, as in the procedure of passive from active.

  

Figure: Elementary trees generated from combining blocks

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