... transitive closure of R and R* denotes the reflexive and transitive closure of R. A context=free grammar G = (N, T, P, S) consists of two finite disjoint sets N and T of nonterminal and terminal ... rules A * al and B * ~2 have a common infix a if al = 1310¢-/1 and a2 = 132(:~-/2, for some 131,132, 71 and -/2. The notion of common infix is an adaptation of the notion of common prefix ... AN EXTENDED THEORY OF HEAD-DRIVEN PARSING Mark-Jan Nederhof * University of Nijmegen Department of Computer Science Toernooiveld, 6525 ED Nijmegen The Netherlands markj an¢cs, kun....