3 research outputs found
Type-driven semantic interpretation and feature dependencies in R-LFG
Once one has enriched LFG's formal machinery with the linear logic mechanisms
needed for semantic interpretation as proposed by Dalrymple et. al., it is
natural to ask whether these make any existing components of LFG redundant. As
Dalrymple and her colleagues note, LFG's f-structure completeness and coherence
constraints fall out as a by-product of the linear logic machinery they propose
for semantic interpretation, thus making those f-structure mechanisms
redundant. Given that linear logic machinery or something like it is
independently needed for semantic interpretation, it seems reasonable to
explore the extent to which it is capable of handling feature structure
constraints as well.
R-LFG represents the extreme position that all linguistically required
feature structure dependencies can be captured by the resource-accounting
machinery of a linear or similiar logic independently needed for semantic
interpretation, making LFG's unification machinery redundant. The goal is to
show that LFG linguistic analyses can be expressed as clearly and perspicuously
using the smaller set of mechanisms of R-LFG as they can using the much larger
set of unification-based mechanisms in LFG: if this is the case then we will
have shown that positing these extra f-structure mechanisms is not
linguistically warranted.Comment: 30 pages, to appear in the the ``Glue Language'' volume edited by
Dalrymple, uses tree-dvips, ipa, epic, eepic, fullnam
Introducing Continuations
This working paper introduces CONTINUATIONS (a concept borrowed from computer science) as a new technique for characterizing certain aspects of the semantics of a natural language. I should emphasize at the outset that this is just an introduction, and that more a rigorous and thorough treatment is under development (see Barker (ms)). In the meantime, this paper mentions certain formal results without proving them, and describes certain new empirical generalizations without exploring them. What it will do is provide an explicit account of a range of familiar phenomena related to quantification, including quantifier scope ambiguity, NP as a scope island, and generalized coordination. What makes the account noteworthy is that it provides a fully and strictly compositional analysis of quantification and generalized coordination that does not rely on syntactic movement operations such as Quantifier Movement, auxiliary storage mechanisms such as Cooper Storage, or type ambiguity as in Hendriks' Flexible Types system
Alternative Phrases Theoretical Analysis and Practical Application
Institute for Communicating and Collaborative Systems"All right, but apart from the sanitation, the medicine, education, wine,
public order, irrigation, roads, the fresh-water system and public health,
what have the Romans ever done for us?"
(Monty Python, The Life of Brian)
Alternative phrases identify selected elements from a set and subject them
to particular scrutiny with respect to the sentence's predicate. For instance, in
the above example, sanitation, medicine, etc. are all identified as elements in
the set of things the Romans have done for us" that should not be included in
the response to the question. They are alternative responses to the desired ones.
Alternative phrases come in a variety of constructions and perform a variety
of tasks: excluding elements (apart from), expressing preference for particular
elements (especially), and simply identifying representative examples (such as).
Not a great deal of work has been done on alternative phrases in general.
Hearst (1992) used a pattern-matching analysis of certain alternative phrases
to learn hyponyms from unannotated corpora. Also, a few examples from a
subset of alternative phrases, called exceptive phrases, have been studied, most
recently, by von Fintel (1993) and Hoeksema (1995). But not all constructions
are amenable to pattern-matching techniques, and the work on exceptive phrases
focuses on some very specific semantic points. The focus of this thesis is to present
a general program for analyzing a wide variety of alternative phrases including
their presuppositional and anaphoric properties.
I perform my analyses in Combinatory Categorial Grammar, a lexicalized
formalism. The semantic aspects of the analysis benefit greatly from the concept
of alternative sets, sets of propositions that differ in one or more argument
(Karttunen and Peters, 1979; Rooth, 1985, 1992; Prevost and Steedman, 1994;
Steedman, 2000a). In addition, elegant solutions are made possible by separating
the semantics into assertion and presupposition (Stalnaker, 1974; Karttunen and
Peters, 1979; Stone and Doran, 1997; Stone and Webber, 1998; Webber et al.,
1999b)| with each performing quite different tasks.
My second goal is to demonstrate the practicality and importance of this analysis to real systems. Although it is relevant to many practical applications,
I will focus primarily on natural language information retrieval (NLIR) as a case
study. In such a domain, queries like Where can I find other web browsers than
Netscape for download? and Where can I find shoes made by Bufialino, such
as the Bushwackers? are often observed. I review several techniques for NLIR
and demonstrate that implementations of those techniques perform poorly on
such queries. I show that understanding alternative phrases can enable simple
techniques which greatly improve precision.
To bridge the gap between these goals, I present Grok, a modular natural
language system. Several general NLP issues necessary to support my linguistic
analysis are discussed: anaphora resolution, processing of presuppositions, interface
to knowledge representation, and the creation of a wide-coverage lexicon.
Special attention is paid to the lexicon, which is a combination of a hand-built
and an acquired lexicon