Generalized context-free grammars

We consider several language generating formalisms from the literature, such as string-valued attribute grammars with only s-attributes, parallel multiple context-free grammars, relational grammars and top-down tree-to-string transducers, of which we have chosen the OnlyS string-valued attribute grammars to be our vantage point. We prove that OnlyS string-valued attribute grammars, parallel multiple context-free grammars and relational grammars generate the same class of languages, and we prove that every language accepted by an OnlyS string-valued attribute grammar is the image of a top-down tree-to-string transducer. The main result of this thesis is the proof of equivalence of the special string-valued attribute grammars, the multiple context-free grammar, the special relational grammar and the nite copying top-down tree-to-string transducer. In order to prove these equivalences, de nitions of some of these formalisms have been slightly modi ed, and normal forms have been (re)de ned and proven. Acknowledgements Working on this thesis has been a great pleasure to me. Of course, I could not do it all on my own. I would like to thank everyone who was interested in my thesis and in the progress I made. In particular Joost Engelfriet, for coming up with this subject for a thesis and for all his suggestions, Hendrik Jan Hoogeboom, who was my supervisor, for all his help and encouraging comments, and Jurriaan Hage, for helping me with correcting, structuring and struggling with proofs that wouldn't work. My very special thanks go out to Jurriaan and Hendrik Jan for always being there when I needed their support.