On Normal Forms and Erasing Rules in Path Controlled Grammars

Abstract

This paper discusses path controlled grammars—context-free gram- mars with a root-to-leaf path in their derivation trees restricted by a control language. First, it investigates the impact of erasing rules on the generative power of path controlled grammars. Then, it establishes two Chomsky-like normal forms for path controlled grammars—the first allows unit rules, the second allows just one erasing rule