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Several grammars have been proposed for modeling RNA pseudoknotted structure. In this paper, we focus on multiple context-free grammars (MCFGs), which are natural extension of context-free grammars and can represent pseudoknots, and extend a specific subclass of MCFGs to a probabilistic model called SMCFG. We present a polynomial time parsing algorithm for(More)
Several grammars have been proposed for modeling RNA pseudoknotted structure. In this paper, we focus on multiple context-free grammars (MCFGs), which are natural extension of context-free grammars and can represent pseudoknots, and extend a specific subclass of MCFGs to a probabilistic model called SMCFG. We present a polynomial time parsing algorithm for(More)
A number of grammatical formalisms were introduced to define the syntax of natural languages. Among them are parallel multiple context-free grammars (pmcfg's) and lexical-functional grammars (lfg's). Pmcfg's and their subclass called multiple context-free grammars (mcfg's) are natural extensions of cfg's, and pmcfg's are known to be recognizable in(More)
Valiant proposed an O(n 2) time algorithm which reduces the recognition problem for context-free languages (CFLs) to the boolean matrices multiplication problem. By this algorithm, the recognition problem for CFLs can be solved in O(maxfn 2 ; M(n)g) time where n is the length of an input string and M(k) is the time needed for multiplying two k k boolean(More)