2,966 research outputs found
Efficient Normal-Form Parsing for Combinatory Categorial Grammar
Under categorial grammars that have powerful rules like composition, a simple
n-word sentence can have exponentially many parses. Generating all parses is
inefficient and obscures whatever true semantic ambiguities are in the input.
This paper addresses the problem for a fairly general form of Combinatory
Categorial Grammar, by means of an efficient, correct, and easy to implement
normal-form parsing technique. The parser is proved to find exactly one parse
in each semantic equivalence class of allowable parses; that is, spurious
ambiguity (as carefully defined) is shown to be both safely and completely
eliminated.Comment: 8 pages, LaTeX packaged with three .sty files, also uses cgloss4e.st
Interaction Grammars
Interaction Grammar (IG) is a grammatical formalism based on the notion of
polarity. Polarities express the resource sensitivity of natural languages by
modelling the distinction between saturated and unsaturated syntactic
structures. Syntactic composition is represented as a chemical reaction guided
by the saturation of polarities. It is expressed in a model-theoretic framework
where grammars are constraint systems using the notion of tree description and
parsing appears as a process of building tree description models satisfying
criteria of saturation and minimality
A Robust Parsing Algorithm For Link Grammars
In this paper we present a robust parsing algorithm based on the link grammar
formalism for parsing natural languages. Our algorithm is a natural extension
of the original dynamic programming recognition algorithm which recursively
counts the number of linkages between two words in the input sentence. The
modified algorithm uses the notion of a null link in order to allow a
connection between any pair of adjacent words, regardless of their dictionary
definitions. The algorithm proceeds by making three dynamic programming passes.
In the first pass, the input is parsed using the original algorithm which
enforces the constraints on links to ensure grammaticality. In the second pass,
the total cost of each substring of words is computed, where cost is determined
by the number of null links necessary to parse the substring. The final pass
counts the total number of parses with minimal cost. All of the original
pruning techniques have natural counterparts in the robust algorithm. When used
together with memoization, these techniques enable the algorithm to run
efficiently with cubic worst-case complexity. We have implemented these ideas
and tested them by parsing the Switchboard corpus of conversational English.
This corpus is comprised of approximately three million words of text,
corresponding to more than 150 hours of transcribed speech collected from
telephone conversations restricted to 70 different topics. Although only a
small fraction of the sentences in this corpus are "grammatical" by standard
criteria, the robust link grammar parser is able to extract relevant structure
for a large portion of the sentences. We present the results of our experiments
using this system, including the analyses of selected and random sentences from
the corpus.Comment: 17 pages, compressed postscrip
Structure preserving transformations on non-left-recursive grammars
We will be concerned with grammar covers, The first part of this paper presents a general framework for covers. The second part introduces a transformation from nonleft-recursive grammars to grammars in Greibach normal form. An investigation of the structure preserving properties of this transformation, which serves also as an illustration of our framework for covers, is presented
Experiences with the GTU grammar development environment
In this paper we describe our experiences with a tool for the development and
testing of natural language grammars called GTU (German:
Grammatik-Testumgebumg; grammar test environment). GTU supports four grammar
formalisms under a window-oriented user interface. Additionally, it contains a
set of German test sentences covering various syntactic phenomena as well as
three types of German lexicons that can be attached to a grammar via an
integrated lexicon interface. What follows is a description of the experiences
we gained when we used GTU as a tutoring tool for students and as an
experimental tool for CL researchers. From these we will derive the features
necessary for a future grammar workbench.Comment: 7 pages, uses aclap.st
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