Single Tree Grammars

Abstract A context-free grammar is a single-tree grammar (STG) if every nonterminal symbol has at most one production rule whose right hand side contains nonterminal symbols. Various properties of this class of grammars are studied. Although most properties of STG's are undecidable, every linear STG generates a bounded language and a deterministic context-free language, so most properties of linear STG's are decidable. Finally, we show that STG grammars have natural applications for logic database query languages.