A text is a tripleτ=(λ,ρ1,ρ2) such that λ is a labeling function, andρ1 andρ2 are linear orders on the domain of λ; hence τ may be seen as a word (λ,ρ1) together with an additional linear orderρ2 on the domain of λ. The orderρ2 is used to give to the word (λ,ρ1) itsindividual hierarchical representation (syntactic structure) which may be a tree but it may be also more general than a tree. In this paper we introducecontext-free grammars for texts and investigate their basic properties. Since each text has its own individual structure, the role of such a grammar should be that of a definition of a pattern common to all individual texts. This leads to the notion of ashapely context-free text grammar also investigated in this paper.
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- [ER1] Ehrenfeucht, A., Rozenberg, G.: Theory of 2-structures, Part I: clans, basic subclasses, and morphisms. Theoret. Comput. Sci.70, 277–303 (1990)Google Scholar
- [ER2] Ehrenfeucht, A., Rozenberg, G.: Theory of 2-structures, Part II: representation through labeled tree families. Theoret. Comput. Sci.70, 305–342 (1990)Google Scholar
- [ER3] Ehrenfeucht, A., Rozenberg, G.: Angular 2-structures. Theoret. Comput. Sci.92, 227–248 (1992)Google Scholar
- [ER4] Ehrenfeucht, A., Rozenberg, G.:T-structures,T-functions, and texts. Theoret. Comput. Sci.116, 227–290 (1993)Google Scholar
- [EPR] Ehrenfeucht, A., Pas, P. ten, Rozenberg, G.: Combinatorial properties of texts. RAIRO, Theoret. Inf. Appl.27, 433–464 (1993)Google Scholar
- [EKR] Ehrig, H., Kreowski, H.-J., Rozenberg, G. (eds.): Graph grammars and their application to computer science (Lect. Notes Comput. Sci., vol. 532) Berlin, Heidelberg, New York: Springer 1990Google Scholar
- [GRS] Graham, R.L., Rothschild, B.L., Spencer, J.H.: Ramsey theory. New York: Wiley 1980Google Scholar
- [S] Salomaa, A.: Formal languages. London, New York: Academic Press 1973Google Scholar