Grammars

Head Driven Phrase Structured Grammar (HPSG)

http://en.wikipedia.org/wiki/Head-driven_phrase_structure_grammar

BNF (Backus-Naur Form)

http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form

Languages and Context-Free Grammars

http://www.gnu.org/software/bison/manual/html_node/Language-and-Grammar.html