167,358 research outputs found

    LTAG semantics with semantic unification

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    This paper sets up a framework for LTAG (Lexicalized Tree Adjoining Grammar) semantics that brings together ideas from different recent approaches addressing some shortcomings of TAG semantics based on the derivation tree. Within this framework, several sample analyses are proposed, and it is shown that the framework allows to analyze data that have been claimed to be problematic for derivation tree based LTAG semantics approaches

    Computing Preferred Answer Sets by Meta-Interpretation in Answer Set Programming

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    Most recently, Answer Set Programming (ASP) is attracting interest as a new paradigm for problem solving. An important aspect which needs to be supported is the handling of preferences between rules, for which several approaches have been presented. In this paper, we consider the problem of implementing preference handling approaches by means of meta-interpreters in Answer Set Programming. In particular, we consider the preferred answer set approaches by Brewka and Eiter, by Delgrande, Schaub and Tompits, and by Wang, Zhou and Lin. We present suitable meta-interpreters for these semantics using DLV, which is an efficient engine for ASP. Moreover, we also present a meta-interpreter for the weakly preferred answer set approach by Brewka and Eiter, which uses the weak constraint feature of DLV as a tool for expressing and solving an underlying optimization problem. We also consider advanced meta-interpreters, which make use of graph-based characterizations and often allow for more efficient computations. Our approach shows the suitability of ASP in general and of DLV in particular for fast prototyping. This can be fruitfully exploited for experimenting with new languages and knowledge-representation formalisms.Comment: 34 pages, appeared as a Technical Report at KBS of the Vienna University of Technology, see http://www.kr.tuwien.ac.at/research/reports

    Modality and expressibility

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    When embedding data are used to argue against semantic theory A and in favor of semantic theory B, it is important to ask whether A could make sense of those data. It is possible to ask that question on a case-by-case basis. But suppose we could show that A can make sense of all the embedding data which B can possibly make sense of. This would, on the one hand, undermine arguments in favor of B over A on the basis of embedding data. And, provided that the converse does not hold—that is, that A can make sense of strictly more embedding data than B can—it would also show that there is a precise sense in which B is more constrained than A, yielding a pro tanto simplicity-based consideration in favor of B. In this paper I develop tools which allow us to make comparisons of this kind, which I call comparisons of potential expressive power. I motivate the development of these tools by way of exploration of the recent debate about epistemic modals. Prominent theories which have been developed in response to embedding data turn out to be strictly less expressive than the standard relational theory, a fact which necessitates a reorientation in how to think about the choice between these theories

    Herstellung eines Phaffia rhodozyma : Stamms mit verstärkter Astaxanthin-Synthese über gezielte genetische Modifikation chemisch mutagenisierter Stämme

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    Ziel dieser Arbeit war es erstmals durch eine Kombination aus chemischer Mutagenese und gezielter genetischer Modifikation (hier: „metabolic engineering“) einen Phaffia-Stamm herzustellen, welcher über die Mutagenese hinaus über eine weiter verstärkte Astaxanthin-Synthese verfügt. Die von „DSM Nutritional Products“ bereitgestellten chemischen Mutanten wurden analysiert und über einen Selektionsprozess auf Pigmentstabilität und Wachstum hin optimiert, da die Stämme aus cryogenisierter Dauerkultur starke Pigmentinstabilitäten und ein verzögertes Wachstum aufwiesen. Über eine exploratorische Phase wurde die Carotinoidsynthese analysiert und festgestellt, dass in den Mutanten keine Einzelreaktionen betroffen sind, welche für die Heraufregulierung der Carotinoidsynthese in den Mutanten verantwortlich sind. Hierbei wurden Limitierungen identifiziert und diese durch Transformation von Expressionsplasmiden mit geeigneten Genen aufgehoben, um damit eine noch effizientere Metabolisierung von Astaxanthin-Vorstufen hin zu Astaxanthin zu erreichen. Eine Überexpression der Phytoensynthase/Lycopinzyklase crtYB resultierte in einem gesteigerten Carotinoidgehalt bei gleichbleibendem Astaxanthin- Anteil. Durch eine zweite Transformation mit einer Expressionskassette für die Astaxanthin-Synthase asy konnte der Carotinoidgehalt weiter gesteigert und zusätzlich eine Limitierung der Metabolisierung von Astaxanthin-Vorstufen behoben werden, sodass die Transformante nahezu alle Intermediate der Astaxanthinsynthese zu Astaxanthin metabolisieren konnte (Gassel et al. 2013). Es konnte gezeigt werden, dass auch in den Mutanten, aus Experimenten mit dem Wildtyp bekannte, Limitierungen identifiziert und ausgeglichen werden konnten

    Modifying (the grammar of) adjuncts : an introduction

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    One aspect of the progress being made is that the focus of attention has widened. Adverbials, though still the heart of the matter, now form part of a much larger set of constituent types subsumed under the general syntactic label of adjunct; while modifier has become the semantic counterpart on the same level of generality. So one of the readings of Modifying Adjuncts stands for the focus on this intersection. Moreover, recent years have seen a number of studies which attest an increasing interest in adjunct issues. There is an impressive number of monographs, e.g. Alexiadou (1997), Laenzlinger (1998), Cinque (1999), Pittner (1999), Ernst (2002), which, by presenting in-depth analyses of the syntax of adjuncts, have sharpened the debate on syntactic theorizing. Serious attempts to gain a broader view on adjuncts are witnessed by several collections, see Alexiadou and Svenonius (2000), Austin, Engelberg and Rauh (in progress); of particular importance are the contributions to vol. 12.1 of the Italian Journal of Linguistics (2000), a special issue on adverbs, the Introductions to which by Corver and Delfitto (2000) and Delfitto (2000) may be seen as the best state-of-the-art article on adverbs and adverbial modification currently on the market. To try and test a fresh view on adjuncts was the leitmotif of the Oslo Conference “Approaching the Grammar of Adjuncts” (Sept 22–25, 1999), which provided the initial forum for the papers contained in this volume and initiated a period of discussion and continuing interaction among the contributors, from which the versions published here have greatly profited. The aim of the Oslo conference, and hence the focus of the present volume, was to encourage syntacticians and semanticists to open their minds to a more integrative approach to adjuncts, thereby paying attention to, and attempting to account for, the various interfaces that the grammar of adjuncts crucially embodies. From this perspective, the present volume is to be conceived of as an interim balance of current trends in modifying the views on adjuncts. In introducing the papers, we will refrain from rephrasing the abstracts, but will instead offer a guided tour through the major problem areas they are tackling. Assessed by thematic convergence and mutual reference, the contributions form four groups, which led us to arrange them into subparts of the book. Our commenting on these is intended (i) to provide a first glance at the contents, (ii) to reveal some of the reasons why adjuncts indeed are, and certainly will remain, a challenging issue, and thereby (iii) to show some facets of what we consider novel and promising approaches
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