369 research outputs found
FUNCTIONAL DEPENDENCIES AND INCOMPLETE INFORMATION
Functional dependencies play an important role in
relational database design. They are defined in the context
of a single relation which at all times must contain
tuples with non-null entries. In this paper we examine
an extension of the functional dependency interpretation
to handle null values, that is, entries in tuples that
represent incomplete information in a relational database.
A complete axiomatization of inference rules for
extended functional dependencies is also presented.
Only after having such results is it possible to talk about
decompositions and normalization theory in a context of
incomplete information. Finally, we show that there are
several practical advantages in using nulls and a weaker
notion of constraint satisfiability.Information Systems Working Papers Serie
Type-driven natural language analysis
The purpose of this thesis is in showing how recent developments in logic programming can be exploited to encode in a computational environment the features of certain linguistic theories. We are in this way able to make available for the purpose of natural language processing sophisticated capabilities of linguistic analysis directly justified by well developed grammatical frameworks.
More specifically, we exploit hypothetical reasoning, recently proposed as one of the possible directions to widen logic programming, to account for the syntax of filler-gap dependencies along the lines of linguistic theories such as Generalized Phrase Structure Grammar and Categorial Grammar. Moreover, we make use, for the purpose of semantic analysis of the same kind of phenomena, of another recently proposed extension, interestingly related to the previous one, namely the idea of replacing first-order terms with the more expressive Ī»-terms of Ī»-Calculus
An Inheritance-Based Theory of the Lexicon in Combinatory Categorial Grammar
Institute for Communicating and Collaborative SystemsThis thesis proposes an extended version of the Combinatory Categorial Grammar
(CCG) formalism, with the following features:
1. grammars incorporate inheritance hierarchies of lexical types, defined over a
simple, feature-based constraint language
2. CCG lexicons are, or at least can be, functions from forms to these lexical types
This formalism, which I refer to as āinheritance-drivenā CCG (I-CCG), is conceptualised
as a partially model-theoretic system, involving a distinction between category
descriptions and their underlying category models, with these two notions being related
by logical satisfaction. I argue that the I-CCG formalism retains all the advantages of
both the core CCG framework and proposed generalisations involving such things as
multiset categories, unary modalities or typed feature structures. In addition, I-CCG:
1. provides non-redundant lexicons for human languages
2. captures a range of well-known implicational word order universals in terms of
an acquisition-based preference for shorter grammars
This thesis proceeds as follows:
Chapter 2 introduces the ābaselineā CCG formalism, which incorporates just the essential
elements of category notation, without any of the proposed extensions. Chapter
3 reviews parts of the CCG literature dealing with linguistic competence in its most
general sense, showing how the formalism predicts a number of language universals
in terms of either its restricted generative capacity or the prioritisation of simpler lexicons.
Chapter 4 analyses the first motivation for generalising the baseline category
notation, demonstrating how certain fairly simple implicational word order universals
are not formally predicted by baseline CCG, although they intuitively do involve
considerations of grammatical economy. Chapter 5 examines the second motivation
underlying many of the customised CCG category notations ā to reduce lexical redundancy,
thus allowing for the construction of lexicons which assign (each sense of)
open class words and morphemes to no more than one lexical category, itself denoted
by a non-composite lexical type.
Chapter 6 defines the I-CCG formalism, incorporating into the notion of a CCG grammar
both a type hierarchy of saturated category symbols and an inheritance hierarchy
of constrained lexical types. The constraint language is a simple, feature-based, highly
underspecified notation, interpreted against an underlying notion of category models
ā this latter point is crucial, since it allows us to abstract away from any particular
inference procedure and focus on the category notation itself. I argue that the partially
model-theoretic I-CCG formalism solves the lexical redundancy problem fairly definitively,
thereby subsuming all the other proposed variant category notations. Chapter 7
demonstrates that the I-CCG formalism also provides the beginnings of a theory of the
CCG lexicon in a stronger sense ā with just a small number of substantive assumptions
about types, it can be shown to formally predict many implicational word order
universals in terms of an acquisition-based preference for simpler lexical inheritance
hierarchies, i.e. those with fewer types and fewer constraints. Chapter 8 concludes the
thesis
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
Dependencies in language: On the causal ontology of linguistic systems
Dependency is a fundamental concept in the analysis of linguistic systems. The many if-then statements offered in typology and grammar-writing imply a causally real notion of dependency that is central to the claim being madeāusually with reference to widely varying timescales and types of processes. But despite the importance of the concept of dependency in our work, its nature is seldom defined or made explicit. This book brings together experts on language, representing descriptive linguistics, language typology, functional/cognitive linguistics, cognitive science, research on gesture and other semiotic systems, developmental psychology, psycholinguistics, and linguistic anthropology to address the following question: What kinds of dependencies exist among language-related systems, and how do we define and explain them in natural, causal terms
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