Let G be a context-free grammar and let L be the language of all the words derived from any variable of G. We prove the following generalization of Higman's theorem: any division order on L is a well quasi-order on L. We also give applications of this result to some quasi-orders associated with unitary grammars. (C) 2004 Elsevier B.V. All rights reserved.
Well quasi-orders and context-free grammars / D'Alessandro, Flavio; Stefano, Varricchio. - In: THEORETICAL COMPUTER SCIENCE. - ISSN 0304-3975. - 327:3(2004), pp. 255-268. (Intervento presentato al convegno 7th International Conference on Developments in Language Theory tenutosi a SZEGED, HUNGARY nel JUL 07-11, 2003) [10.1016/j.tcs.2004.03.069].
Well quasi-orders and context-free grammars
D'ALESSANDRO, Flavio;
2004
Abstract
Let G be a context-free grammar and let L be the language of all the words derived from any variable of G. We prove the following generalization of Higman's theorem: any division order on L is a well quasi-order on L. We also give applications of this result to some quasi-orders associated with unitary grammars. (C) 2004 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
