Talk:Boolean grammar

This page only references very recent papers (2002 and on), but boolean grammars and an efficient recognizer for them was described at least as early as 1988 by Heilbrunner, in "An efficient recognizer for the Boolean closure of context-free languages", see http://www.sciencedirect.com/science/article/pii/030439759190205G for the full text PDF of the page (no charge, open access). In case it is not clear, yes, the definition of "the Boolean closure of context-free languages" is *exactly* equivalent to the definition "Boolean Grammars", just with different notation.