Extended attribute grammars (EAGs) are a reformulation of Knuth's attribute grammars, suggested by Watt and Madsen in 1977. Although clearly not adaptive by my definition, EAGs are important for their conceptual role in the development of Christiansen grammars (and thus, indirectly, of RAGs). They also figure prominently in my speculations on the nature of grammar.
EAGs differ from Knuth's original model in three ways:
It is also possible to view EAGs as a kind of two-level grammar. The rule forms generate an infinite set of rule instances, which may be treated as the rule set of an infinite context-free grammar whose nonterminals are the attributed nonterminals of the EAG. (There seems to me to be a difference in emphasis, however, between EAGs, which fall within the philosophical tradition of attribute grammars, and e.g. van Wijngaarden grammars, which have always had a separate tradition.)
There's a much more extensive treatment of EAGs in my Master's thesis.
Offline sources: The original paper is [Watt 77], the principal reference used here is [Mads 80].