A Simple Transformation for ONine-Parsable Grammars and its Termination Properties

A b s t r a c t We present, in easily reproducible terms, a simple t ransformat ion for offline-parsable grammars which results in a provably te rmina t ing parsing program directly top-down interpretable in Prolog. The t ransformat ion consists in two steps: (1) removal of empty-product ions, followed by: (2) left-recursion el imination. It is related bo th to left-corner parsing (where the g rammar is compiled, ra ther than interpreted through a parsing program, and with the advantage of guaranteed te rmina t ion in the presence of empty productions) and to the Generalized Greibach Normal Form for I)CGs (with the advantage of implementa t ion simplicity).