Indexed languages

Indexed languages correspond to:

• Indexed grammar
• Macro grammars, see M. J. Fischer. Grammars with Macro-Like Productions, 1968
• NSA
• 2-iterated pushdown automata, see J. Engelfriet and H. Vogler. Pushdown Machines for the Macro Tree Transducer, 1986

Open questions

• Does Indexed include all Conjuctive languages?
• Does Indexed include all Context free with lookahead?
• Does Indexed include all ConjLa?