The AGFL formalism for the syntactic description of Natural Languages has been developed by the Computer Science Department of the Radboud University of Nijmegen. It is a formalism in which large context free grammars can be described in a compact way. AGFLs belong to the family of two level grammars, along with attribute grammars and DCG's: a first, context-free level is augmented with set-valued features for expressing agreement between constituents.
Source: wiktionary