5 research outputs found

    Syntax-Directed Translations and Quasi-alphabetic Tree Bimorphisms - Revisited

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    Quasi-alphabetic tree bimorphisms [Steinby, Tîrn uc : Dening syntax-directed translations by tree bimorphisms. Theor. Comput. Sci., to appear. http://dx.doi.org/10.1016/j.tcs.2009.03.009, 2009] are reconsidered. It is known that the class of (string) translations dened by such bimorphisms coincides with the class of syntaxdirected translations. This result is extended to a smaller class of tree bimorphisms namely (linear and complete) symbol-to-symbol tree bimorphisms. Moreover, it is shown that the class of simple syntax-directed translations coincides with the class of translations dened by alphabetic tree bimorphisms (also known as nite-state relabelings). This proves that alphabetic tree bimorphisms are not suciently powerful to model all syntax-directed translations. Finally, it is shown that the class of tree transformations dened by quasi-alphabetic tree bimorphisms is closed under composition. The corresponding result is known in the variable-free case
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