The Free On-line Dictionary of Computing (30 December 2018):

Extended Affix Grammar
EAG

    (EAG) A formalism for describing both the
   context free syntax and the context sensitive syntax of
   languages.

   EAGs belong to the family of two-level grammars.  They are
   very closely related to two-level van Wijngaarden grammars.

   EAG can be used as a specification formalism, specifying in
   relations rather than functions, or as a relational
   programming language like PROLOG.

   (http://www.cs.ru.nl/~kees/eag/)

   (2009-02-06)