 Like Van Wijngaarden grammars, EAGs have "hyperrules" that form a context-free grammar except in that their nonterminals may have arguments, known as "affixes", the possible values of which are supplied by another context-free grammar, the "metarules".EAGs were introduced and studied by D.A.Watt in 1974; recognizers were developed at the University of Nijmegen between 1985 and 1995.