Abstract
The following generalization of a well-known result in tree acceptors is established. For each context-free grammarG and tree acceptor\(\mathfrak{A}\) there exists a strict interpretationG′ ofG and a yield-preserving projection π′ from the trees over the alphabet ofG′ into the trees over the alphabet ofG such that\(\pi '(D_{G'} ) = D_G \cap T(\mathfrak{A})\),D G andD G′ being the derivation trees ofG′ andG respectively and\(T(\mathfrak{A})\) the trees accepted by\(\mathfrak{A}\). Moreover, ifG is unambiguous, then (a)G′ can be chosen unambiguous, and (b) there is an unambiguous strict interpretationG″ ofG such thatL(G″)=L(G)−L(G′).
Zusammenfassung
BezeichnetD G die Menge der Ableitungsbäume einer kontextfreien GrammatikG und\(T(\mathfrak{A})\) die Menge der von einem endlichen Baumautomaten\(\mathfrak{A}\) akzeptierten Bäume, dann gilt: Zu jeder kontextfreien GrammatikG und jedem Baumautomaten\(\mathfrak{A}\) existiert eine strikte InterpretationG′ vonG und eine Yield-erhaltende Projektion π′ der Bäume über dem Alphabet vonG′ in die Menge der Bäume über dem Alphabet vonG derart, daß\(\pi '(D_{G'} ) = D_G \cap T(\mathfrak{A})\). Dies verallgemeinert ein bekanntes Resultat über Baumtransduktoren. Weiter wird gezeigt, daß im Falle einer eindeutigen GrammatikG zusätzlich gilt: (a) FürG′ kann ebenfalls eine eindeutige Grammatik gewählt werden, und (b) es existiert eine strikte InterpretationG″ vonG mitL(G″)=L(G)−L(G′).
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References
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This author was supported in part by the National Science Foundation under Grant MCS-77-22323.
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Ginsburg, S., Mayer, O. Tree acceptors and grammar forms. Computing 29, 1–9 (1982). https://doi.org/10.1007/BF02254847
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DOI: https://doi.org/10.1007/BF02254847