Categorial grammars with iterated types form a strict hierarchy of k-valued languages

Denis Béchet, Alexandre Dikovsky, Annie Foret
2012 Theoretical Computer Science  
The notion of k-valued categorial grammars in which every word is associated to at most k types is often used in the field of lexicalized grammars as a fruitful constraint for obtaining interesting properties like the existence of learning algorithms. This constraint is reasonable only when the classes of k-valued grammars correspond to a real hierarchy of generated languages. Such a hierarchy has been established earlier for the classical categorial grammars. In this paper the hierarchy by the
more » ... k-valued constraint is established in the class of categorial grammars extended with iterated types adapted to express the so called projective dependency structures.
doi:10.1016/j.tcs.2012.04.024 fatcat:h6enqz7pefekxigaeo2mv65rru