Van wijngaarden grammars and space complexity class EXSPACE

SummaryTop-down and bottom-up decision strategies for van Wijngaarden grammars led to type R and type L van Wijngaarden grammars. The corresponding language families are now shown to be equal and, furthermore, to equal EXSPACE. Thus, EXSPACE is characterised syntactically, and the closure properties of type L and type R languages are those of EXSPACE.