Context-sensitive grammar

About: Context-sensitive grammar is a research topic. Over the lifetime, 1938 publications have been published within this topic receiving 45911 citations. The topic is also known as: CSG.

A context-free superset approximation of unification-based grammars

Abstract: We present a simple and intuitive approximation method for turning unification-based grammars into context-free grammars. We apply our method to several grammars and report on the quality of the approximation. We also present several methods that speed up the approximation process and that might be interesting to other areas of unification-based processing. Finally, we introduce a novel disambiguation method for unification grammars which is based on probabilistic context-free approximations.

Grammars with Composite Storages

Abstract: Linear indexed grammars (LIGs) can be used to describe nonlocal dependencies. The indexing mechanism, however, can only account for dependencies that are nested. In natural languages one can easily find examples to which this simple model cannot be applied straightforwardly. In this paper I will show that a formalism fitting better to linguistic structures can be obtained by using a sequence of pushdowns instead of one pushdown for the storage of the indices in a derivation. Crucially, we have to avoid unwanted interactions between the push-downs that would make possible the simulation of a turing machine. [1] solves this problem for multi-pushdown automata by restricting reading to the first nonempty pushdown. I will argue that the corresponding restriction on writing is more natural from a linguistic point of view. I will show that, under each of both restrictions, grammars with a sequence of n pushdowns give rise to a subclass of the nth member of the hierarchy defined by [15,16], and therefore are mildly context sensitive.

A hierarchy result for random forbidding context picture grammars

Abstract: We use random context picture grammars to generate pictures through successive refinement. The productions of such a grammar are context-free, but their application is regulated — "permitted" or "forbidden" — by context randomly distributed in the developing picture. Grammars using this relatively weak context often succeed where context-free grammars fail, e.g. in generating the Sierpinski carpets. On the other hand it proved possible to develop iteration theorems for three subclasses of these grammars, namely a pumping–shrinking, a pumping and a shrinking lemma for context-free, random permitting and random forbidding context picture grammars, respectively. Finding necessary conditions is problematic in the case of most models of context-free grammars with context-sensing ability, since they consider a variable and its context as a finite connected array. We have already shown that context-free picture grammars are strictly weaker than both random permitting and random forbidding context picture grammars, also that random permitting context is strictly weaker than random context. We now show that grammars which use forbidding context only are strictly weaker than random context picture grammars.