Sublinear Parallel Time Recognition of Tree Adjoining Language

A parallel algorithm is presented for recognizing the class of languages generated by tree adjoining grammars, a tree rewriting system which has applications in computational Linguistics. This class of languages is known to properly include all context-free languages; for example, the non-context-free sets {anbncn} and {ww) are in this class. It is shown that the recognition problem for tree adjoining languages can be solved by a concurrent-read, exclusive-write parallel random-access machine (CREW PRAM) in 0 (log2(n)) time using polynomially many processors. This extends a previous result for context-free languages.