scholarly journals On the Maximal Number of Complete Extensions in Abstract Argumentation Frameworks

2021 ◽  
Author(s):  
Markus Ulbricht
Keyword(s):  
Expressive Power ◽  
Research Area ◽  
Formal Proof ◽  
Knowledge Representation And Reasoning ◽  
Intrinsic Properties ◽  
Lower And Upper Bounds ◽  
Major Research ◽  
Exact Bound ◽  
Abstract Argumentation ◽  
Points Of View

Abstract argumentation frameworks are by now a major research area in knowledge representation and reasoning. Various aspects of AFs have been extensively studied over the last 25 years. Contributing to understanding the expressive power of AFs, researchers found lower and upper bounds for the maximal number of extensions, that is, acceptable points of view, in AFs. One of the classical and most important concepts in AFs are so-called complete extensions. Surprisingly, the exact bound for the maximal number of complete extensions in an AF has not yet been formally established, although there is a reasonable conjecture tracing back at least to 2015. Recently the notion of modularization was introduced and it was shown that this concept plays a key role for the understanding of relations between semantics as well as intrinsic properties. In this paper, we will use this property to give a formal proof of the conjecture regarding complete semantics.

scholarly journals On Cycles, Attackers and Supporters --- A Contribution to The Investigation of Dynamics in Abstract Argumentation

2021 ◽  
Author(s):  
Ringo Baumann ◽  
Markus Ulbricht
Keyword(s):  
Knowledge Representation ◽  
Main Part ◽  
Research Area ◽  
Knowledge Representation And Reasoning ◽  
Major Research ◽  
Abstract Argumentation ◽  
Odd Cycle ◽  
The Impact ◽  
Odd Cycles

Abstract argumentation as defined by Dung in his seminal 1995 paper is by now a major research area in knowledge representation and reasoning. Dynamics of abstract argumentation frameworks (AFs) as well as syntactical consequences of semantical facts of them are the central issues of this paper. The first main part is engaged with the systematical study of the influence of attackers and supporters regarding the acceptability status of whole sets and/or single arguments. In particular, we investigate the impact of addition or removal of arguments, a line of research that has been around for more than a decade. Apart from entirely new results, we revisit, generalize and sum up similar results from the literature. To gain a comprehensive formal and intuitive understanding of the behavior of AFs we put special effort in comparing different kind of semantics. We concentrate on classical admissibility-based semantics and also give pointers to semantics based on naivity and weak admissibility, a recently introduced mediating approach. In the second main part we show how to infer syntactical information from semantical one. For instance, it is well-known that if a finite AF possesses no stable extension, then it has to contain an odd-cycle. In this paper, we even present a characterization of this issue. Moreover, we show that the change of the number of extensions if adding or removing an argument allows to conclude the existence of certain even or odd cycles in the considered AF without having further information.

scholarly journals Revisiting the Foundations of Abstract Argumentation – Semantics Based on Weak Admissibility and Weak Defense

2020 ◽  
Vol 34 (03) ◽  
pp. 2742-2749
Author(s):  
Ringo Baumann ◽  
Gerhard Brewka ◽  
Markus Ulbricht
Keyword(s):  
Classical Case ◽  
Research Area ◽  
Major Research ◽  
Abstract Argumentation ◽  
New Concepts ◽  
Key Concepts ◽  
Problematic Issue ◽  
Rigorous Study ◽  
Grounded Semantics ◽  
Special Case

In his seminal 1995 paper, Dung paved the way for abstract argumentation, a by now major research area in knowledge representation. He pointed out that there is a problematic issue with self-defeating arguments underlying all traditional semantics. A self-defeat occurs if an argument attacks itself either directly or indirectly via an odd attack loop, unless the loop is broken up by some argument attacking the loop from outside. Motivated by the fact that such arguments represent self-contradictory or paradoxical arguments, he asked for reasonable semantics which overcome the problem that such arguments may indeed invalidate any argument they attack. This paper tackles this problem from scratch. More precisely, instead of continuing to use previous concepts defined by Dung we provide new foundations for abstract argumentation, so-called weak admissibility and weak defense. After showing that these key concepts are compatible as in the classical case we introduce new versions of the classical Dung-style semantics including complete, preferred and grounded semantics. We provide a rigorous study of these new concepts including interrelationships as well as the relations to their Dung-style counterparts. The newly introduced semantics overcome the issue with self-defeating arguments, and they are semantically insensitive to syntactic deletions of self-attacking arguments, a special case of self-defeat.

scholarly journals Synthesizing Argumentation Frameworks from Examples

2019 ◽  
Vol 66 ◽  
pp. 503-554 ◽  
Author(s):  
Andreas Niskanen ◽  
Johannes Wallner ◽  
Matti Järvisalo
Keyword(s):  
Natural Extension ◽  
Research Abstract ◽  
Expressive Power ◽  
Synthesis Problem ◽  
Constraint Optimization ◽  
Abstract Argumentation ◽  
Central Notion ◽  
Definition Of ◽  
The Given ◽  
Representation Formalism

Argumentation is today a topical area of artificial intelligence (AI) research. Abstract argumentation, with argumentation frameworks (AFs) as the underlying knowledge representation formalism, is a central viewpoint to argumentation in AI. Indeed, from the perspective of AI and computer science, understanding computational and representational aspects of AFs is key in the study of argumentation. Realizability of AFs has been recently proposed as a central notion for analyzing the expressive power of AFs under different semantics. In this work, we propose and study the AF synthesis problem as a natural extension of realizability, addressing some of the shortcomings arising from the relatively stringent definition of realizability. In particular, realizability gives means of establishing exact conditions on when a given collection of subsets of arguments has an AF with exactly the given collection as its set of extensions under a specific argumentation semantics. However, in various settings within the study of dynamics of argumentation---including revision and aggregation of AFs---non-realizability can naturally occur. To accommodate such settings, our notion of AF synthesis seeks to construct, or synthesize, AFs that are semantically closest to the knowledge at hand even when no AFs exactly representing the knowledge exist. Going beyond defining the AF synthesis problem, we study both theoretical and practical aspects of the problem. In particular, we (i) prove NP-completeness of AF synthesis under several semantics, (ii) study basic properties of the problem in relation to realizability, (iii) develop algorithmic solutions to NP-hard AF synthesis using the constraint optimization paradigms of maximum satisfiability and answer set programming, (iv) empirically evaluate our algorithms on different forms of AF synthesis instances, as well as (v) discuss variants and generalizations of AF synthesis.

The Disciplines of Reason and Lyric Poetry

2014 ◽  
Author(s):  
Rivkah Zim
Keyword(s):  
Real World ◽  
Lyric Poetry ◽  
Expressive Power ◽  
The Real ◽  
Points Of View

This chapter demonstrates how Boethius' text established many of the themes and forms that spoke to and for later writers in prison. These include: consolation from the expressive power of ordered lyric meters set against the disorder of injustice and suffering in the real world; the importance of a well-stocked mind and imagination in maintaining resistance to oppression; and the expressive potential of paradox in reconciling apparent contraries and celebrating the creativity that may arise under situations of adversity. The text also promoted the subtle simplicity of dialectic and patterns of opposing binaries used to resolve impossible tensions in apparently progressive forms of logical argument and related forms of dialogic exchange between different points of view represented in argument, correspondence, and intertextual allusiveness. Finally, it demonstrated the urgent need often experienced in the condemned cell to set the record straight (to name names) or to construct a memorial image of the authorial self and, more objectively, to testify for humankind by offering insights derived from the prisoner's experience.

A systematic analysis of identity based encryption (IBE)

2021 ◽  
Vol 25 (3) ◽  
pp. 343-356
Author(s):  
Aravind Karrothu ◽  
Jasmine Norman
Keyword(s):  
Research Area ◽  
Resource Constraint ◽  
Security Threats ◽  
Light Weight ◽  
Future Trends ◽  
Major Research ◽  
Systematic Analysis ◽  
Identity Based Encryption ◽  
Wide Range ◽  
Identity Based

Light-weight cryptography is a major research area due to the minimization of the size of the devices utilized for such services. The associated security threats do increase as their applications are more now. Identity-Based Encryption (IBE) with its wide range of cryptographic schemes and protocols is specifically found suitable for low-end devices that have much resource constraint. This work describes various schemes and protocols in IBE. In this paper an analysis of IBE schemes and the various attacks they are prone to are discussed. The future trends are found to be very promising and challenging.

Probabilistic Models for the Semantic Web

2010 ◽  
pp. 74-105 ◽  
Author(s):  
Livia Predoiu
Keyword(s):  
Semantic Web ◽  
Knowledge Representation ◽  
Classical Logic ◽  
Probabilistic Models ◽  
Expressive Power ◽  
Knowledge Representation And Reasoning ◽  
Uncertain Information ◽  
New Approaches ◽  
The Web

Recently, there has been an increasing interest in formalisms for representing uncertain information on the Semantic Web. This interest is triggered by the observation that knowledge on the web is not always crisp and we have to be able to deal with incomplete, inconsistent and vague information. The treatment of this kind of information requires new approaches for knowledge representation and reasoning on the web as existing Semantic Web languages are based on classical logic which is known to be inadequate for representing uncertainty in many cases. While different general approaches for extending Semantic Web languages with the ability to represent uncertainty are explored, we focus our attention on probabilistic approaches. We survey existing proposals for extending semantic web languages or formalisms underlying Semantic Web languages in terms of their expressive power, reasoning capabilities as well as their suitability for supporting typical tasks associated with the Semantic Web.

scholarly journals 50 nm Scale Alignment Method for Hybrid Manufacturing Processes for Full 3D Structuring

2020 ◽  
Vol 21 (12) ◽  
pp. 2407-2417
Author(s):  
Ki-Hwan Jang ◽  
Hae-Sung Yoon ◽  
Hyun-Taek Lee ◽  
Eunseob Kim ◽  
Sung-Hoon Ahn
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Research Area ◽  
Manufacturing Processes ◽  
Alignment Error ◽  
Alignment Method ◽  
Major Research ◽  
Hybrid Processes

AbstractIn micro-/nano-scale, multi-material three-dimensional (3D), structuring has been a major research area for making various applications. To overcome dimensional and material limitations, several hybrid processes have been proposed. The hybrid processes were performed in the same or different numerically controlled stages. If the stages differed, the substrate was moved and locked to the stage before fabrication. During the locking, alignment error occurred. This error became problematic because this significantly compromised the quality of final structures. Here, an alignment method for a hybrid process consisted of a focused ion beam milling, aerodynamically focused nanoparticle printing, and micro-machining was developed. Two sets of collinear marks were placed at the edges of the substrate. Rotational and translational errors were calculated and compensated using the marks. Processes having different scales were bridged through this alignment method. Various materials were utilized, and accuracy was less than 50 nm when the length of the substrate was less than 13 mm. The alignment method was employed to fabricate a V-shaped structure and step-shaped structure using polymer, ceramic, and metal.

Diffraction, crystallography and microscopy beyond three dimensions: structural dynamics in space and time

2004 ◽  
Vol 363 (1827) ◽  
pp. 315-329 ◽  
Author(s):  
Ahmed H. Zewail
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Gas Phase ◽  
Structural Dynamics ◽  
Research Area ◽  
Three Dimensions ◽  
Ultrafast Electron Diffraction ◽  
Major Research ◽  
Condensed Media ◽  
Recent Developments

In this article we highlight recent developments of ultrafast electron diffraction and crystallography at Caltech. These developments have made it possible to resolve transient structures, both spatially (0.01 Å) and temporally (picosecond and now femtosecond), in the gas phase and condensed media—surfaces, interfaces, and crystals—with wide-ranging applications. With the extension to ultrafast electron microscopy, discussed here and elsewhere, we present an overview of one major research area at our centre, the Laboratory for Molecular Sciences.

scholarly journals To be or not to be: the early history of H 3 and H 3 +

2012 ◽  
Vol 370 (1978) ◽  
pp. 5225-5235 ◽  
Author(s):  
Helge Kragh
Keyword(s):  
Quantum Chemistry ◽  
Research Area ◽  
Early History ◽  
Active Hydrogen ◽  
Major Research ◽  
New Methods ◽  
History Of

Triatomic hydrogen became a major research area only after 1980, but its history goes back to J. J. Thomson’s discovery in 1911. In fact, the possible existence of H 3 was suggested as early as 1895. This paper outlines the history of H 3 and up to the mid-1930s, when chemists and physicists ceased to believe in the existence of the H 3 molecule. In the intervening years, there was a great deal of interest in ‘active hydrogen’ and also in the configuration of H 3 , which was examined by Bohr in 1919. While H 3 was abandoned, was not. Although the properties of were largely unknown, the existence of the ion was firmly established, and its structure studied by means of the new methods of quantum chemistry.

scholarly journals Towards Electrochemical Water Desalination Techniques: A Review on Capacitive Deionization, Membrane Capacitive Deionization and Flow Capacitive Deionization

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 96 ◽  
Author(s):  
Gbenro Folaranmi ◽  
Mikhael Bechelany ◽  
Philippe Sistat ◽  
Marc Cretin ◽  
Francois Zaviska
Keyword(s):  
Brackish Water ◽  
Research Area ◽  
Water Desalination ◽  
Ion Adsorption ◽  
Capacitive Deionization ◽  
Major Research ◽  
Modus Operandi ◽  
Solvated Ions ◽  
The 1960S ◽  
Simple Potential

Electrochemical water desalination has been a major research area since the 1960s with the development of capacitive deionization technique. For the latter, its modus operandi lies in temporary salt ion adsorption when a simple potential difference (1.0–1.4 V) of about 1.2 V is supplied to the system to temporarily create an electric field that drives the ions to their different polarized poles and subsequently desorb these solvated ions when potential is switched off. Capacitive deionization targets/extracts the solutes instead of the solvent and thus consumes less energy and is highly effective for brackish water. This paper reviews Capacitive Deionization (mechanism of operation, sustainability, optimization processes, and shortcomings) with extension to its counterparts (Membrane Capacitive Deionization and Flow Capacitive Deionization).

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