João José Neto

Adaptive automata for context-dependent languages

The present paper introduces the concept of adaptive automata as an alternative formal tool for describing context-dependent languages. This formal framework has the advantage of allowing easy mapping of a language description into an efficient parser for that language. Such a good performance is due to the potential hierarchical structure adaptive automata may exhibit, allowing natural construction of acceptors no more complex than strictly needed by each particular language. Efficiency is also due to the way adaptive automata operate, by changing according to its input, including and discarding transitions as needed to parse the particular input text adaptive automata start from an initial self-modifying version, and evolve through a path of intermediate configurations until a final configuration is reached, when the source text is exhausted. The evolution from an automatons configuration to the next one may be designed to occur strictly when a construct is found which is not recognized by the current configuration of the automaton. So, one may view the acceptance of a particular sentence as a sequence of recognitions of its substrings, each operated by the corresponding configuration of the adaptive automaton. That offers a practical way for efficiently accepting context-dependent languages in a purely syntactical way, allowing full treatment for syntactical aspects of the language such as dynamic syntax and the socalled static semantics. Then, the use of adaptive automata brings the possibility of handling in a purelly syntactical way several autentically syntactical concepts, such as predefined words, symbol-tables, scoping, type-checking, argument-to-parameter matching, macro definitions and expansions, syntax macros for defining new language constructs, and many others, usually treated semantically, or resolved outside the parser.

Adaptive Rule-Driven Devices - General Formulation and Case Study

A formal device is said to be adaptive whenever its behavior changes dynamically, in a direct response to its input stimuli, without interference of external agents, even its users. In order to achieve this feature, adaptive devices have to be self-modifiable. In other words, any possible changes in the devices behavior must be known at their full extent at any step of its operation in which the changes have to take place. Therefore, adaptive devices must be able to detect all situations causing possible modifications and to adequately react by imposing corresponding changes to the devices behavior. In this work, devices are considered whose behavior is based on the operation of subjacent non-adaptive devices that be fully described by some finite set of rules. An adaptive rule-driven device may be obtained by attaching adaptive actions to the rules of the subjacent formulation, so that whenever a rule is applied, the associated adaptive action is activated, causing the set of rules of the subjacent non-adaptive device to be correspondingly changed. In this paper a new general formulation is proposed that unifies the representation and manipulation of adaptive rule-driven devices and states a common framework for representing and manipulating them. The main feature of this formulation is that it fully preserves the nature of the underlying non-adaptive formalism, so that the adaptive resulting device be easily understood by people familiar to the subjacent device. For illustration purposes, a two-fold case-study is presented, describing adaptive decision tables as adaptive rule-driven devices, and using them for emulating the behavior of a very simple adaptive automaton, which is in turn another adaptive rule-driven device.

Adaptive automata: a revisited proposal

This paper impose further discipline to the use of adaptive automata [Jos94], [Iwa00] by restricting some of their features, in order to obtain devices that are easier to create and more readable, without loosing computational power. An improved notation is proposed as a first try towards a language for adaptive paradigm programming.

An experiment on handshape Sign recognition using adaptive technology: Preliminary results

This paper presents an overview of current work on the recognition of sign language and a prototype of a simple editor for a small subset of the Brazilian Sign Language, LIBRAS. Handshape based alphabetical signs, are captured by a single digital camera, processed on-line by using computational vision techniques and converted to the corresponding Latin letter. The development of such prototype employed a machine-learning technique, based on automata theory and adaptive devices. This technique represents a new approach to be used in the far more complex problem of full LIBRAS recognition. As it happens with spoken languages, sign languages are not universal. They vary a lot from country to country, and in spite of the existence of many works in American Sign Language (ASL), the automatic recognition of Brazilian Sign Language has not been extensively studied. ...

Solving Complex Problems Efficiently with Adaptive Automata

Adaptive technologies [1] are based on the self-modifying property of some systems, which give their users a powerful facility for expressing and handling complex problems. One may turn a rule-based formalism into a corresponding adaptive one by attaching adaptive actions to their rules. This work focuses adaptive automata, and adaptive formalism based on structured pushdown automata. Its transitions may hold adaptive actions responsible for self-modifications. An example ilustrates an adaptive-automata-based solution to an example problem focusing the copy language, an interesting context-dependent language.

Decision Tree Induction using Adaptive FSA

This paper introduces a new algorithm for the induction of decision trees, based on adaptive techniques. One of the main feature of this algorithm is the application of automata theory to formalize the problem of decision tree induction and the use of a hybrid approach, which integrates both syntactical and statistical strategies. Some experimental results are also presented indicating that the adaptive approach is useful in the construction of ecien t learning algorithms.

Using adaptive formalisms to describe context-dependencies in natural language

This text sketches a method based on adaptive technology for representing context-dependencies in NL processing. Based on a previous work [4] dedicated to syntactical ambiguities and nondeterminisms in NL handling we extend it to consider context-dependencies not previously addressed. Although based on the powerful adaptive formalism [3], our method relies on adaptive structured pushdown automata [1] and grammars [2] - resulting simplicity, low-cost and efficiency.

An Adaptive Framework for the Design of Software Specification Languages

Software has been specified as domain theories. A useful strategy for building specifications is the incremental extension of an initial theory, in which increments add new terms and notions not considered in previous extensions. Given an increment, the corresponding theory is stated in a corresponding specification language. The next increment — or extension of the theory — typically requires a related language extension, which has been specified in a variety of ways, e.g. meta-computations, rewriting systems, etc. Adaptive devices naturally support such scheme, whose instances should reflect the impact of extension variations on the specification language. This paper describes an adaptive framework for the design of a class of software specification languages supporting the incremental process of elaborating software specifications.

Adaptive automata for mapping unknown environments by mobile robots

Robotic mapping is one of the most important requirements for a truly autonomous mobile robot. Mobile robots should be able to building abstract representation of the physical environment, in order to navigate and work in such environment. This paper presents an adaptive way to make such representation. The proposed system allows the robot to explore all the environment and acquire the information incoming from the sensors (presence or absence of obstacles) while it travels. The robot may start the mapping process at any point of the space to be mapped. Due to the adaptability of the chosen method, the process has the capability of dynamically increase the memory requirements according to the already mapped area, even without any a priori knowledge of the environment.

WTA 2007 - I.1 - A small survey of the evolution of Adaptivity and Adaptive Technology

The present paper is an attempt to survey the evolution of adaptivity and its applications. In this context, adaptivity is a term that refers to the property exhibited by some system or device that is able to self-modify its own set of operation rules, driven exclusively by its history, without the help of any external active element. Adaptive technology refers to the application of adaptivity as a tool for solving practical problems. This paper gathers a significant collection of available publications on adaptivity and related topics. It organizes the collected works according to their subject, and the publications on each subject, according to the chronological sequence of their publication.