Formal language

About: Formal language is a research topic. Over the lifetime, 5763 publications have been published within this topic receiving 154114 citations.

Expressivity in Polygonal, Plane Mereotopology

Abstract: In recent years, there has been renewed interest in the development of formal languages for describing mereological (part-whole) and topological relationships between objects in space. Typically, the non-logical primitives of these languages are properties and relations such as ‘ x is connected’ or ‘ x is a part of y ’, and the entities over which their variables range are, accordingly, not points , but regions : spatial entities other than regions are admitted, if at all, only as logical constructs of regions. This paper considers two first-order mereotopological languages, and investigates their expressive power. It turns out that these languages, notwithstanding the simplicity of their primitives, are surprisingly expressive. In particular, it is shown that infinitary versions of these languages are adequate to express (in a sense made precise below) all topological relations over the domain of polygons in the closed plane.

On the Complexities of Linear LL(1) and LR(1) Grammars

Abstract: Several notions of deterministic linear languages are considered and compared with respect to their complexities and to the families of formal languages they generate. We exhibit close relationships between simple linear languages and the deterministic linear languages both according to Nasu and Honda and to Ibarra, Jiang, and Ravikumar. Deterministic linear languages turn out to be special cases of languages generated by linear grammars restricted to LL(1) conditions, which have a membership problem solvable in NC1. In contrast to that, deterministic linear languages defined via automata models turn out to have a DSPACE(logn)-complete membership problem. Moreover, they coincide with languages generated by linear grammars subject to LR(1) conditions.

Weighted picture automata and weighted logics

Abstract: The theory of two-dimensional languages, generalizing formal string languages, was motivated by problems arising from image processing and models of parallel computing. Weighted automata and series over pictures map pictures to some semiring and provide an extension to a quantitative setting. We establish a notion of a weighted MSO logics over pictures. The semantics of a weighted formula will be a picture series. We introduce weighted 2-dimensional online tessellation automata (W2OTA) extending the common automata-theoretic model for picture languages. We prove that the class of picture series defined by sentences of the weighted logics coincides with the family of picture series that are computable by W2OTA. Moreover, behaviours of W2OTA coincide precisely with the recognizable picture series characterized in [18].

On embedded languages for model management

Abstract: The authors present a technique called embedded languages which is a generalization of the EML (executable modeling language) approach. They believe that this technique can prove extremely useful in implementing desirable features not found in existing systems. The approach is discussed with reference to an advanced model management system, TEFA, which is being developed on the basis of this technique. >

Nonmonotonic Reasoning with Well Founded Semantics.

Abstract: Well Founded Semantics is adequate to capture nonmonotonic reasoning if we interpret the Well Founded model of a program P as a (possibly incomplete) view of the world. Thus the Well Founded model may be accepted to be a definite view of the world and the extended stable models as alternative enlarged consistent belief models an agent may have about the world. Our purpose is to exhibit a modular systematic method of representing nonmonotonic problems with the Well Founded semantics of logic programs. In this paper we use this method to represent and solve some classical nonmonotonic problems. This leads us to consider our method quite generic.