In order to be able to capture effects from co-transcriptional folding, we extend stochastic context-free grammars such that the probability of applying a rule can depend on the length of the subword that is eventually generated from the symbols introduced by the rule, and we show that existing algorithms for training and for determining the most probable parse tree can easily be adapted to the...

An attractive mechanism to specify global constraints in rostering and other domains is via formal languages. For instance, the REGULAR and GRAMMAR constraints specify constraints in terms of the languages accepted by an automaton and a context-free grammar respectively. Taking advantage of the fixed length of the constraint, we give an algorithm to transform a context-free grammar into an auto...

We improve an existing propagator for the context-free grammar constraint and demonstrate experimentally the practicality of the resulting propagator. The underlying technique could be applied to other existing propagators for this constraint. We argue that constraint programming solvers are more suitable than existing solvers for verification tools that have to solve string constraints, as the...

We investigate a new type of finite copying parallel rewriting system, i.e., grammars with linked nonterminals, which extend the generative capacity of context-free grammars. They can be thought of as having sentential forms where some instances of a nonterminal may be linked. The context-free-like productions replace a nonterminal together with its connected instances. New links are only estab...

Bisimulation equivalence is decidable in polynomial time over normed graphs generated by a context-free grammar. We present a new algorithm, working in time O(n5), thus improving the previously known complexity O(n8polylog(n)). It also improves the previously known complexity O(n6polylog(n)) of the equality problem for simple grammars. Digital Object Identifier 10.4230/LIPIcs.FSTTCS.2010.1

The equivalence problem for context-free grammars is “given two arbitrary grammars, do they generate the same language ?” Since this is undecidable in general attention has been restricted to decidable subclasses of the context-free grammars. For example, the classes of U(k) grammars and real-time strict deterministic grammars. In this paper it is shown that the equivalence problem for U-regula...

This paper describes a model of syntactical analysis. It shows first how a context-free grammar formalism can be modified in order to reduce the number of rules required by a natural language, and second, how this formalism can be extended to the handling of some non-context-free phenomena. The description of the algorithm is also given. The process of discontinuous constituents is performed by...

Are propagating scattered context grammars as powerful as context sensitive grammars? This question customarily referred to as the L (PSCG) = L (CS) (see [4]) problem, represents a long standing open problem in formal language theory. The present paper reformulates and answers this question in terms of CD grammar systems. More precisely, the paper introduces CD grammar systems whose components ...

A polynomial-time procedure is presented for deciding bisimilarity of normed context-free processes. It follows as a corollary that language equivalence of simple context-free grammars is decidable in polynomial time.

We introduce the notion of a differentiation function of a context-free grammar which gives the number of terminal words that can be derived in a certain number of steps. A grammar is called narrow (or k-narrow) iff its differentiation function is bounded by a constant (by k). We present the basic properties of differentiation functions, especially we relate them to structure function of contex...