I t is wel] known tha t context-sensitive languages can be generated by means of monotonic grammars (see Ginsburg, Greibach, 1966) i.e. grammars whose rules have the form f --~ g, where I f ] , the length of f, is not greater than I g I . Such a g rammar generates the language, but almost no grammatical structure of the language is given. When such a structure is also investigated the original ...

Tree controlled grammars are context-free grammars where the associated language only contains those terminal words which have a derivation where the word of any level of the corresponding derivation tree belongs to a given regular language. We present some results on the power of such grammars where we restrict the regular languages to some known subclasses of the family of regular languages.

We study the compressed word problem: a variant of the word problem for finitely generated groups where the input word is given by a context-free grammar that generates exactly one string. We show that finite extensions and free products preserve the complexity of the compressed word problem. Also, the compressed word problem for a graph group can be solved in polynomial time. These results all...

Let A be a finite, totally ordered alphabet, and let P be the lexicographic ordering on A*. Let X be a subset of A*. The language of minimal words of X is the subset of X composed of the lexicographically minimal word of X for each length: Min(X)=[x # X | \w # X, |w|=|x| O xPw]. The aim of this paper is to prove that if L is a context-free language, then the language Min(L) context-free. ] 1997

In this paper we describe a method of translating a Lambek grammar with one division into an equivalent context-free grammar whose size is bounded by a polynom from the size of the original grammar. Earlier constructions by Buszkowski and Pentus lead to exponential growth of the grammar size. 1 Lambek Grammars and Context-Free Gram-

We prove a Chomsky-Schützenberger representation theorem for weighted multiple context-free languages.

We consider conditional context-free grammars that generate languages of nite index. Thereby, we solve an open problem stated in Dassow and PP aun's monograph on regulated rewriting. Moreover, we show that conditional context-free languages with context-free conditions of nite index are more powerful than conditional context-free languages with regular conditions of nite index. Furthermore, we ...

We study k-prefix-free, k-suffix-free and k-infix-free languages that generalize prefix-free, suffix-free and infix-free languages by allowing marginal errors. For example, a string x in a k-prefix-free language L can be a prefix of up to k different strings in L. Namely, a code (language) can allow some marginal errors. We also define finitely prefix-free languages in which a string x can be a...

The family of one-rule grid semi-Thue systems, introduced by Alfons Geser, is the family of one-rule semi-Thue systems such that there exists a letter c that occurs as often in the left-hand side as the right-hand side of the rewriting rule. We prove that for any one-rule grid semi-Thue system S, the set S(w) of all words obtainable from w using repeatedly the rewriting rule of S is a construct...