| TR#: | CS0044 |
| Class: | CS |
| Title: | Theory Of W-languages; Part I: Characterizations Of W-context Free Languages |
| Authors: | Rina S.Cohen and Arie Y.Gold |
| CS0044.pdf | |
| Abstract: | An w-language is a set consisting of w-type strings over some alphabet. This paper introduces the basic notions concerning generation of w-languages by means of w-grammars and their recognition by w-machines of various types. Attention is then focused on W-CFL's, the w-languages generated by w-context free grammars. Two main characterizations of the family of W-CFL' s are ob tained: a) An w-language is an w-CFL if and only if n W' t can be represented as .u UiVi' where for each i = l, •••n, Ui and 1-i Vi are context free languages. This result gener4lizes McNaughton's characterization of w-regular languages [Mc]. b) w-CFL' s are precisely the w-languages recognized by w-pushdown automata by designated state sets (and also by "emptying" the pushdown store infinitely many times). A few other characterizations and normal forms for the w-CFL's are given and several decidability results, e.g. the solvability of the emptiness problem, are established. |
| Copyright | The above paper is copyright by the Technion, Author(s), or others. Please contact the author(s) for more information |
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