1265	 On the Relative Efficiencies of Context-Free Grammar Recognizers	 A number of diverse recognition procedures that have been proposed for parsing sentences with respect to a context-free grammar are described in this paper by means of a common device. Each procedure is defined by giving an algorithm for obtaining a nondeterministic Turing Machine recognizer that is equivalent to a given context-free grammar. The formalization of the Turing Machine has been chosen to make possible particularly simple description of the parsing procedures considered. An attempt has been made to compare recognition efficiencies for the procedures defined. For a few simple grammars and sentences a formal comparison has been made. Empirical comparison of the recognition of more realistic programming languages such as LISP and ALGOL has been made by means of a program which simulates the Turing Machine on the Univac M- computer. Several algorithms for producing grammars equivalent to a given context-free grammar have been considered and the increase in recognition efficiency they afford has been empirically investigated.
