Dealing with non-termination in DCGs

The objective of this paper is to study a practical approach to deal with non-termination in de nite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical e ciency and operational completeness. In order to guarantee the validity of our conclusions, we rst map our study to a common situated framework, where the e ectiveness of each approach will be examined and, later, compared by running experiments.Eje: TeoríaRed de Universidades con Carreras en Informática (RedUNCI

Dealing with non-termination in DCGs

The objective of this paper is to study a practical approach to deal with non-termination in de nite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical e ciency and operational completeness. In order to guarantee the validity of our conclusions, we rst map our study to a common situated framework, where the e ectiveness of each approach will be examined and, later, compared by running experiments.Eje: TeoríaRed de Universidades con Carreras en Informática (RedUNCI

Dealing with non-termination in DCGs

The objective of this paper is to study a practical approach to deal with non-termination in de nite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical e ciency and operational completeness. In order to guarantee the validity of our conclusions, we rst map our study to a common situated framework, where the e ectiveness of each approach will be examined and, later, compared by running experiments.Eje: TeoríaRed de Universidades con Carreras en Informática (RedUNCI

M. Vilares Ferro

The objective of this paper is to study a practical approach to deal with nontermination in definite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical efficiency and operational completeness. In order to guarantee the validity of our conclusions, we first map our study to a common situated framework, where the effectiveness of each approach will be examined and, later, compared by running experiments.

An Operational Model for Parsing Fixed-Mode DCGs

Logic programs share with context-free grammars a strong reliance on well-formedness conditions. Their proof procedures can be viewed as a generalization of context-free parsing. In particular, definite clause grammars can be interpreted as an extension of the classic context-free formalism where the notion of finite set of non-terminal symbols is generalized to a possibly infinite domain of directed graphs. In this case, standard polynomial parsing methods may no longer be applicable as they can lead to gross inefficiency or even non-termination for the algorithms. We briefly present a proposal to avoid these drawbacks. We choose to work in the context of fixed-mode programs, focusing on two aspects: Avoiding limitations on the parsing process, and extending the unification to composed terms without overload for non-cyclic structures. Key Words: DCG, Dynamic Programming, Logical Push-Down Automaton, Cyclic Term. 1 A parsing strategy for DCGs Strategies for executing definite clause ..

A Comparison for Unification-Based Parsers

Unification-based grammars have been the object of study in computational linguistics over the last few years with the intention of creating powerful parsing environments. However, it is not common to find practical studies about what the real interest of these techniques is, and which approaches are better adapted in each case. We attempt to justify the practical consideration of dynamic programming in the continuum of Horn-like formalisms, showing that conclusions attained for definite clause grammars are a natural extension of the same conclusions in contextfree theory. Our aim is to demonstrate the practical interest of this technology, suggesting a simple decision guide for the interested reader. Keywords: Parsing, dynamic programming, push-down automata, static analysis, structure sharing. 1 Introduction Highly redundant computations are a characteristic drawback in non-deterministic parsing, as is the case in natural language processing (NLP). We shall differentiate between tw..

On Integration of Parsing and Tree Matching Schemes

In this paper, we present a proposal intended to demonstrate the applicability of tabulation techniques to pattern recognition problems, when we deal with structures sharing some common parts. This work is motivated by the study of information retrieval for textual databases, using pattern matching as a basis for querying data. To attain this goal, we study the existing relationship between parsing schema and tree-to-tree correction in a dynamic programming frame. As a result, we describe an algorithm that efficiently profits from sharing in syntactic structures.

GALENA: Tabular DCG Parsing for Natural Languages

We present a definite clause based parsing environment for natural languages, whose operational model is the dynamic interpretation of logical push-down automata. We attempt to briefly explain our design decisions in terms of a set of properties that practical natural language processing systems should incorporate. The aim is to show both the advantages and the drawbacks of our approach. 1 Introduction Logic programming have been extensively used to analyze natural languages [5] due to its declarativeness, the possibility of expressing partial information via variables, the ability of expressing linguistic knowledge as a deductive process and the important role that logic have played in linguistics to represent natural language semantics. Several grammar formalisms have been developed into the realm of logic programming but we restrict this discussions to one of them, definite clause grammars [9] (DCGs), although the results can be applied to other logical formalisms. DCGs can be cons..