Paper: Parsing With Semidirectional Lambek Grammar Is NP-Complete

ACL ID P96-1013
Title Parsing With Semidirectional Lambek Grammar Is NP-Complete
Venue Annual Meeting of the Association of Computational Linguistics
Session Main Conference
Year 1996
Authors

We study the computational complexity of the parsing problem of a variant of Lambek Categorial Grammar that we call semidirectional. In semidirectional Lambek calculus SD[ there is an additional non- directional abstraction rule allowing the formula abstracted over to appear any- where in the premise sequent's left-hand side, thus permitting non-peripheral ex- traction. SD[ grammars are able to gen- erate each context-free language and more than that. We show that the parsing prob- lem for semidireetional Lambek Grammar is NP-complete by a reduction of the 3- Partition problem.