9,000 research outputs found
Parsing with Typed Feature Structures
In this paper we provide for parsing with respect to grammars expressed in a
general TFS-based formalism, a restriction of ALE. Our motivation being the
design of an abstract (WAM-like) machine for the formalism, we consider parsing
as a computational process and use it as an operational semantics to guide the
design of the control structures for the abstract machine.
We emphasize the notion of abstract typed feature structures (AFSs) that
encode the essential information of TFSs and define unification over AFSs
rather than over TFSs. We then introduce an explicit construct of multi-rooted
feature structures (MRSs) that naturally extend TFSs and use them to represent
phrasal signs as well as grammar rules. We also employ abstractions of MRSs and
give the mathematical foundations needed for manipulating them. We then present
a simple bottom-up chart parser as a model for computation: grammars written in
the TFS-based formalism are executed by the parser. Finally, we show that the
parser is correct.Comment: PostScript, 15 pages; Proc. 4th Intl. Workshop on Parsing
Technologies, Prague, September 199
An Abstract Machine for Unification Grammars
This work describes the design and implementation of an abstract machine,
Amalia, for the linguistic formalism ALE, which is based on typed feature
structures. This formalism is one of the most widely accepted in computational
linguistics and has been used for designing grammars in various linguistic
theories, most notably HPSG. Amalia is composed of data structures and a set of
instructions, augmented by a compiler from the grammatical formalism to the
abstract instructions, and a (portable) interpreter of the abstract
instructions. The effect of each instruction is defined using a low-level
language that can be executed on ordinary hardware.
The advantages of the abstract machine approach are twofold. From a
theoretical point of view, the abstract machine gives a well-defined
operational semantics to the grammatical formalism. This ensures that grammars
specified using our system are endowed with well defined meaning. It enables,
for example, to formally verify the correctness of a compiler for HPSG, given
an independent definition. From a practical point of view, Amalia is the first
system that employs a direct compilation scheme for unification grammars that
are based on typed feature structures. The use of amalia results in a much
improved performance over existing systems.
In order to test the machine on a realistic application, we have developed a
small-scale, HPSG-based grammar for a fragment of the Hebrew language, using
Amalia as the development platform. This is the first application of HPSG to a
Semitic language.Comment: Doctoral Thesis, 96 pages, many postscript figures, uses pstricks,
pst-node, psfig, fullname and a macros fil
Amalia -- A Unified Platform for Parsing and Generation
Contemporary linguistic theories (in particular, HPSG) are declarative in
nature: they specify constraints on permissible structures, not how such
structures are to be computed. Grammars designed under such theories are,
therefore, suitable for both parsing and generation. However, practical
implementations of such theories don't usually support bidirectional processing
of grammars. We present a grammar development system that includes a compiler
of grammars (for parsing and generation) to abstract machine instructions, and
an interpreter for the abstract machine language. The generation compiler
inverts input grammars (designed for parsing) to a form more suitable for
generation. The compiled grammars are then executed by the interpreter using
one control strategy, regardless of whether the grammar is the original or the
inverted version. We thus obtain a unified, efficient platform for developing
reversible grammars.Comment: 8 pages postscrip
TDL--- A Type Description Language for Constraint-Based Grammars
This paper presents \tdl, a typed feature-based representation language and
inference system. Type definitions in \tdl\ consist of type and feature
constraints over the boolean connectives. \tdl\ supports open- and closed-world
reasoning over types and allows for partitions and incompatible types. Working
with partially as well as with fully expanded types is possible. Efficient
reasoning in \tdl\ is accomplished through specialized modules.Comment: Will Appear in Proc. COLING-9
Constraint Logic Programming for Natural Language Processing
This paper proposes an evaluation of the adequacy of the constraint logic
programming paradigm for natural language processing. Theoretical aspects of
this question have been discussed in several works. We adopt here a pragmatic
point of view and our argumentation relies on concrete solutions. Using actual
contraints (in the CLP sense) is neither easy nor direct. However, CLP can
improve parsing techniques in several aspects such as concision, control,
efficiency or direct representation of linguistic formalism. This discussion is
illustrated by several examples and the presentation of an HPSG parser.Comment: 15 pages, uuencoded and compressed postscript to appear in
Proceedings of the 5th Int. Workshop on Natural Language Understanding and
Logic Programming. Lisbon, Portugal. 199
An integrated architecture for shallow and deep processing
We present an architecture for the integration of shallow and deep NLP components which is aimed at flexible combination of different language technologies for a range of practical current and future applications. In particular, we describe the integration of a high-level HPSG parsing system with different high-performance shallow components, ranging from named entity recognition to chunk parsing and shallow clause recognition. The NLP components enrich a representation of natural language text with layers of new XML meta-information using a single shared data structure, called the text chart. We describe details of the integration methods, and show how information extraction and language checking applications for realworld German text benefit from a deep grammatical analysis
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