Results 11  20
of
36
Ordering Constraints over Feature Trees Expressed in Secondorder Monadic Logic
 Information and Computation
, 1998
"... The language FT of ordering constraints over feature trees has been introduced as an extension of the system FT of equality constraints over feature trees. While the firstorder theory of FT is well understood, only few decidability results are known for the firstorder theory of FT . We introduc ..."
Abstract

Cited by 8 (4 self)
 Add to MetaCart
The language FT of ordering constraints over feature trees has been introduced as an extension of the system FT of equality constraints over feature trees. While the firstorder theory of FT is well understood, only few decidability results are known for the firstorder theory of FT . We introduce a new method for proving the decidability of fragments of the firstorder theory of FT . This method is based on reduction to second order monadic logic that is decidable according to Rabin's famous tree theorem. The method applies to any fragment of the firstorder theory of FT for which one can change the model towards sufficiently labeled feature trees  a class of trees that we introduce. As we show, the first ordertheory of ordering constraints over sufficiently labeled feature trees is equivalent to secondorder monadic logic (S2S for infinite and WS2S for finite feature trees). We apply our method for proving that entailment of FT with existential quantifiers j 1 j=9x 1 : : :9x n j 2 is decidable. Previous results were restricted to entailment without existential quantifiers which can be solved in cubic time. Meanwhile, entailment with existential quantifiers has been shown PSPACEcomplete (for finite and infinite feature trees respectively).
Rijke. Describing and querying semistructured data: Some expressiveness results
 Advances in Databases, LNCS
, 1998
"... Data in traditional relational and objectoriented databases is highly structured and subject to explicit schemas. Lots of data, for example on the worldwide web is only semistruetured. There may be some regularities, but not all data need adhere to it, and the format itself may be subject to frequ ..."
Abstract

Cited by 6 (1 self)
 Add to MetaCart
Data in traditional relational and objectoriented databases is highly structured and subject to explicit schemas. Lots of data, for example on the worldwide web is only semistruetured. There may be some regularities, but not all data need adhere to it, and the format itself may be subject to frequent change. The important issues in the area of semistructured data are: how to describe (or constrain) semistructured data, and how to query it. It is generally agreed that the appropriate data model for semistructured data is an edgelabeled graph, but beyond that there are many competing proposals. Various constraint languages and query languages have been proposed, but what is lacking so far are 'sound theoretical foundations, possibly a logic in the style of relational calculus. So, there is a need for more works on calculi for semistructured data and algebraizations of these calculi ' [Abiteboul 1997]. One of the main methodological points of this paper is the following. There are many areas in computer science and beyond in which describing and reasoning about finite graphs is a key issue. There exists a large body of work in areas
Path Constraints on Deterministic Graphs
, 1998
"... We study path constraints for deterministic graph model [9], a variation of semistructured data model in which data is represented as a rooted edgelabeled directed graph with deterministic edge relations. The path constraint languages considered include the class of word constraints introduced in [ ..."
Abstract

Cited by 6 (3 self)
 Add to MetaCart
(Show Context)
We study path constraints for deterministic graph model [9], a variation of semistructured data model in which data is represented as a rooted edgelabeled directed graph with deterministic edge relations. The path constraint languages considered include the class of word constraints introduced in [4], the language P c investigated in [8], and an extension of P c defined in terms of regular expressions. Complexity results on the implication and finite implication problems for these constraint languages are established. 1 Introduction Semistructured data is characterized as having no type constraints, irregular structure and rapidly evolving or missing schema [1, 6]. Examples of such data can be found on the WorldWide Web, in biological databases and after data integration. In particular, documents of XML (eXtensible Markup Language [5]) can also be viewed as semistructured data [10]. The unifying idea in modeling semistructured data is the representation of data as an edgelabeled, r...
Type Inference for FirstClass Messages with Feature Constraints
 International Journal of Foundations of Computer Science
, 1998
"... We present a constraint system OF of feature trees that is appropriate to specify and implement type inference for firstclass messages. OF extends traditional systems of feature constraints by a selection constraint xhyiz "by firstclass feature tree" y, in contrast to the standard sel ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
We present a constraint system OF of feature trees that is appropriate to specify and implement type inference for firstclass messages. OF extends traditional systems of feature constraints by a selection constraint xhyiz "by firstclass feature tree" y, in contrast to the standard selection constraint x[ f ]y "by fixed feature" f . We investigate the satisfiability problem of OF and show that it can be solved in polynomial time, and even in quadratic time in an important special case. We compare OF with Treinen's constraint system EF of feature constraints with firstclass features, which has an NPcomplete satisfiability problem. This comparison yields that the satisfiability problem for OF with negation is NPhard. Based on OF we give a simple account of type inference for firstclass messages in the spirit of Nishimura's recent proposal, and we show that it has polynomial time complexity: We also highlight an immediate extension that is desirable but makes type inference NPhard.
Typedriven semantic interpretation and feature dependencies in RLFG
, 1998
"... This paper describes a new formalization of LexicalFunctional Grammar called RLFG (where the "R" stands for "Resourcebased"). The formal details of RLFG are presented in Johnson (1997); the present work concentrates on motivating RLFG and explaining to linguists how it diffe ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
This paper describes a new formalization of LexicalFunctional Grammar called RLFG (where the "R" stands for "Resourcebased"). The formal details of RLFG are presented in Johnson (1997); the present work concentrates on motivating RLFG and explaining to linguists how it differs from the "classical" LFG framework presented in Kaplan and Bresnan (1982). This work is largely a reaction to the linear logic semantics for LFG developed by Dalrymple and colleagues (Dalrymple et al., 1995, 1996a,b,c). As explained below, it seems to me that their "glue language" approach bears a partial resemblance to those versions of Categorial Grammar which exploit the CurryHoward correspondence to obtain semantic intepretation (van Benthem, 1995), such as Lambek Categorial Grammar and its descendants. A primary goal of this work is to develop a version of LFG in which this connection is made explicit, and in which semantic interpretation falls out as a byproduct of the CurryHoward correspondence rather than needing to be stipulated via semantic interpretation rules. Once one has enriched LFG's formal machinery with the linear logic mechanisms needed for semantic interpretation, it is natural to ask whether these make any existing components of LFG redundant. As Dalrymple and her colleagues note, LFG's fstructure completeness and coherence constraints fall out as a byproduct of the linear logic machinery they propose for semantic interpretation, thus making those fstructure 2 Chapter 1. Typedriven semantic interpretation and feature dependencies in RLFG 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 con...
Formal & computational aspects of dependency grammar : Heads, dependents, and dependency structures. http://www.coli.unisb.de/g̃j/Lectures/DG.ESSLLI/index.phtml
, 2002
"... ..."
(Show Context)
The Categorial FineStructure of Natural Language
, 2003
"... Categorial grammar analyzes linguistic syntax and semantics in terms of type theory and lambda calculus. A major attraction of this approach is its unifying power, as its basic function/argument structures occur across the foundations of mathematics, language and computation. This paper considers, i ..."
Abstract

Cited by 3 (1 self)
 Add to MetaCart
Categorial grammar analyzes linguistic syntax and semantics in terms of type theory and lambda calculus. A major attraction of this approach is its unifying power, as its basic function/argument structures occur across the foundations of mathematics, language and computation. This paper considers, in a light examplebased manner, where this elegant logical paradigm stands when confronted with the wear and tear of reality. Starting from a brief history of the Lambek tradition since the 1980s, we discuss three main issues: (a) the fit of the lambda calculus engine to characteristic semantic structures in natural language, (b) the coexistence of the original typetheoretic and more recent modal interpretations of categorial logics, and (c) the place of categorial grammars in the complex total architecture of natural language, which involves  amongst others  mixtures of interpretation and inference.
Semantics for AttributeValue Theories
, 1999
"... ersion `x such that the father of x is a plumber', using variables as formalized pronouns. Writing `fx j . . . x . . . g' for `x such that . . . x . . . ', it can be rendered into `fx j P (yF yx)g', with `F ' for `fxy j x is father of yg' and `P ' for `plumber&apos ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
ersion `x such that the father of x is a plumber', using variables as formalized pronouns. Writing `fx j . . . x . . . g' for `x such that . . . x . . . ', it can be rendered into `fx j P (yF yx)g', with `F ' for `fxy j x is father of yg' and `P ' for `plumber'. Elimination of the denite description leads to: fx j 9y(Fyx ^ Py) ^ 8yz(Fyx ^ F zx ! y = z)g . Presupposing `F ' as functional, that is, 8xyz(Fxz ^ Fyz ! x =<F12.24
Parallelism Constraints in Underspecified Semantics
, 2002
"... der Universit"at des Saarlandes ..."
(Show Context)