A Practical Method for the Implementation of Syntactic Parsers

Abstract:- The implementation of syntactic parsers is a very important task in compiler construction. There are several classic methods and algorithms used for syntactic parser construction [1][2][3][4][5]. In [3] there is a proposal of a method for the automatic construction of syntax acceptors from context-free grammars, and also a first extension of this method in order to allow the generation of syntax trees while accepting input sentences. In this paper we present a further extension of that method by including the addition of semantic actions to the generated device. This is a very practical method which can be used for educational purposes, by means of a step-by-step construction and understanding of each algorithm applied to the original grammar. Moreover, the transducer representing the desired parser activates semantic actions while a syntactic parsing tree is automatically generated for the given input sentence. Key-Words:- context-free languages, automata, grammars, syntax, parser, syntax tree, automatic generation

Adaptative rule-driven devices - general formulation anda 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 device’s 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 device’s 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

Anais do XXVI Congresso da SBC WSO l III Workshop de Sistemas Operacionais New Visual Characterization Graphs for Memory System Analysis and Evaluation

Abstract. The characterization of workloads used in memory systems analysis and evaluation is important to detect factors in programs which may or may not favor the performance of each potential system configuration. In this paper, by suggesting the use of simple and functional graphs, we demonstrate that it is possible to visually get, with considerable precision, a number of relevant information about memory access characteristics. The new proposed graphs are useful both to document related experiments, in terms of memory access patterns and locality of references in workloads, and to foresee the performance of distinct memory systems. Applications of locality analysis include the improvement upon algorithms for memory management and techniques for program optimization

2 Laboratório de Engenharia de Software – Departamento de Informática

Abstract. Research in knowledge representation has explored several formalisms with logical and probabilistic features. In this paper we present three tools that support the development of probabilistic logic knowledge bases. The first tool is a generator of probabilistic propositional satisfiability (PSAT) problems that is useful in testing algorithms. The second tool is an consistency checker for PSAT that handles probabilities over CNFs. The third tool is a convenient editor for PSAT problems that simplifies the construction of knowledge bases. Resumo. A pesquisa em representação de conhecimento têm explorado diversos formalismos envolvendo aspectos lógicos e probabilísticos. Neste artigo apresentamos três ferramentas que dão suporte ao desenvolvimento de bases de conhecimento lógico-probabilísticas. A primeira ferramenta é um gerador de problemas de satisfatibilidade probabilística proposicional (PSAT), que é útil para testar algoritmos. A segunda ferramenta é um verificador de consistência em PSAT que lida com probabilidades sobre CNFs. A terceira ferramenta é um editor de problemas PSAT que simplifica a construção de bases de conhecimento. 1