Regular Description of Context-free Graph Languages
نویسندگان
چکیده
منابع مشابه
Regular Description of Context-Free Graph Languages
A set of (labeled) graphs can be de ned by a regular tree language and one regular string language for each possible edge label, as follows. For each tree t from the regular tree language the graph gr(t) has the same nodes as t (with the same labels), and there is an edge with label from node x to node y if the string of labels of the nodes on the shortest path from x to y in t belongs to the r...
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In this paper we consider two questions. First we consider whether every pattern language which is regular can be generated by a regular pattern. We show that this is indeed the case for extended (erasing) pattern languages if alphabet size is at least four. In all other cases, we show that there are patterns generating a regular language which cannot be generated by a regular pattern. Next we ...
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A graph language L is in the class C-edNCE of context-free edNCE graph languages if and only if L = f(T) where f is a function on graphs that can be deened in monadic second-order logic and T is the set of all trees over some ranked alphabet. This logical characterization implies a large number of closure and decidability properties of the context-free edNCE graph languages. Rather than context...
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We investigate regular realizability (RR) problems, which are the problems of verifying whether the intersection of a regular language – the input of the problem – and a fixed language, called a filter, is non-empty. In this paper we focus on the case of context-free filters. The algorithmic complexity of the RR problem is a very coarse measure of the complexity of context-free languages. This ...
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ژورنال
عنوان ژورنال: Journal of Computer and System Sciences
سال: 1996
ISSN: 0022-0000
DOI: 10.1006/jcss.1996.0087