Polarized dependency (PD-) grammars are proposed as a means of efficient treatment of discontinuous constructions. PD-grammars describe two kinds of dependencies : local, explicitly derived by the rules, and long, implicitly specified by negative and positive valencies of words. If in a PD-grammar the number of non-saturated valencies in derived structures is bounded by a constant, then it is weakly equivalent to a cf-grammar and has a
Alexander Ja. Dikovsky