Showing papers on "Indexed language published in 1999"

The synthesis of language learners

Abstract: An index for an r.e. class of languages (by definition) is a procedure which generates a sequence of grammars defining the class. An index for an indexed family of languages (by definition) is a procedure which generates a sequence of decision procedures defining the family. Studied is the metaproblem of synthesizing from indices for r.e. classes and for indexed families of languages various kinds of language learners for the corresponding classes or families indexed. Many positive results, as well as some negative results, are presented regarding the existence of such synthesizers. The negative results essentially provide lower bounds for the positive results. The proofs of some of the positive results yield, as pleasant corollaries, subset-principle or tell-tale style characterizations for the learnability of the corresponding classes or families indexed. For example, the indexed families of recursive languages that can be behaviorally correctly identified from positive data are surprisingly characterized by Angluin's condition 2 (the subset principle for circumventing overgeneralization).

Restarting automata, Church-Rosser languages, and representations of r.e. languages.

Abstract: Apparatus and method for molding generally cubical building modules of concrete, the apparatus comprising both internal and external movably mounted molding components and preferably including mechanisms for advancing the components into molding position and for withdrawing the components from the molding position upon completion of the molding of a module. The method involves the use of such molding components and contemplates certain sequences in the advancement and withdrawal of the molding components for different portions of the modules. The outside mold parts comprise superimposed horizontal strips and alternative screw jack and reciprocating rod devices are provided for mounting and sequentially advancing and withdrawing the outside mold strips. Provision is further made for subjecting the concrete cast in the side walls to vibration.

Strong Iteration Lemmata for Regular, Linear, Context-Free, and Linear Indexed Languages

Abstract: New iteration lemmata are presented, generalizing most of the known iteration lemmata for regular, linear, context-free, and linear indexed languages.

Grammatical inference for the automatic generation of visual languages

Abstract: In this paper we address the problem of the automatic generation of visual languages from a sample set of visual sentences. We present an improvement of the inference module of the VLG system which was originally conceived for the generation of iconic languages [11]. With this extension any kind of visual languages, like diagrams and forms, can be considered. To this aim, we present an inference algorithm for the class of Boundary SR grammars. These grammars are a subclass of the SR grammars with the interesting property of confluence, which extends the concept of context-freeness to the case of nonlinear grammars. Moreover, in spite of the simplicity and naturalness of the formalism, the generative power of this class is sufficient to specify interesting visual languages. The inference algorithm exploits an elegant characterization of Boundary SR languages in terms of tree and string languages. More precisely, we show that a visual language is a Boundary SR language if and only if it can be defined as a regular tree language and a set of properly associated string languages. Based on this result, the problem of identifying structural properties in a diagrammatic visual sentence is brought back to the detection of structural properties in tree and string languages. The main advantage coming from the use of a grammatical inference technique in visual language specification is that the designer only needs to specify a set of visual sentences that he/she feels to sufficiently exemplify the intended target language.

Timed languages, dyadic approximations and regular tree grammars

Abstract: Our research on the modelization of the loop actionperception for an autonomous robot has led us naturally towards a tree-like representation of that interaction: a node is labeled by a perceptive context of the robot, the different branches correspond to the various available actions and the children nodes are then the effect of these different actions on the original context. This tree-like view allows us to state rigorously the problems of viable control in terms of games: the existence of a controller is reduced to the existence of strategies which allow to walk through the trees representing the system in order to remain within a given class of contexts (viability goal). Such game approaches are widely used in computer science (BL69; Mos89; NYY92), and appear in hybrid control theory too (TLS98). Furthermore it is necessary to describe these tree sets as simply as possible, in order to decide for the existence of a controller, and in the best case to synthesize such a controller (The95). In this paper, we study timed automata from the point of view of regular tree grammars showing how our approach can be applied to this central class of decidable hybrid systems.