1,721,111 research outputs found
An Ontology of Exceptions for Knowledge Representation
No full textDefeasible reasoning is a kind of reasoning where some generalisations may not be valid in all circumstances, that is, general conclusions may fail in some cases. Various formalisms have been developed to model this kind of reasoning, especially characteristic of common-sense contexts. However, it is not easy for a modeller to choose a formalism that is a good fit for a particular domain from an ontological point of view. In this paper, we present a framework for formulating the characteristics of defeasibility and reasoning with exceptions which exploits and incorporates related fields of inquiry, including generics, ceteris paribus laws, and a truthmaking theory for generalisations. The resulting theory allows a grounded comparison of the various formalisms and reveals their ontological commitments. To illustrate and apply this framework, we compare the main systems of non-monotonic logics, showing the differences that may occur from an ontological perspective
Defeasible Reasoning in Description Logics with Prototype Descriptions
No full textDefeasible reasoning has always been a central interest of researchers in the fields of Artificial Intelligence (AI) and Multi-Agent Systems (MAS). In fact, this kind of reasoning is central to dealing with conflicting knowledge or beliefs that agents may hold without causing inconsistencies. In the context of languages for Knowledge Representation, many formal approaches have been proposed specifically in Description Logics (DLs) to deal with this phenomenon. With a perspective towards human-centred and agentive AI and building on the DL paradigm we pursue an approach informed by results coming from fields such as linguistics, philosophy and cognitive science. A central problem in the general area of defeasible DLs is to give a principled solution to the question of where preferences originate from in order to provide a notion of defeasibility. To address this issue, a core aspect of our approach is to compute preferences from the knowledge presented in a knowledge base (with standard semantics) itself. We thus present a non-monotonic DL based on a combination of ideas from prototype theory, weighted DLs (aka ‘tooth logic’), and earlier work on justifiable exceptions. A central ingredient in the new framework is the notion of a prototype description, i.e. weighted characterisations of concepts based on the typical features of its members. We show that through such descriptions it is possible to compute a typicality score which allows to define a preference order over models, useful to solve conflicts across exceptional instances. We define two principle ways of computing such preferences, discuss some core semantic properties and finally outline a translation into Answer Set Programming
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Know Your Exceptions: Towards an Ontology of Exceptions in Knowledge Representation
No full textDefeasible reasoning is a kind of reasoning where some generalisations
may not be valid in all circumstances, that is general conclusions may fail in some
cases. Various formalisms have been developed to model this kind of reasoning,
which is characteristic of common-sense contexts. However, it is not easy for a
modeller to choose among these systems the one that better fits its domain from an
ontological point of view.
In this paper we first propose a framework based on the notions of exceptionality
and defeasibility in order to be able to compare formalisms and reveal their ontological commitments. Then, we apply this framework to compare four systems,
showing the differences that may occur from an ontological perspective
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Asymmetric Hybrids: Dialogues for Computational Concept Combination
Full text linkWhen people combine concepts these are often characterised as “hybrid”, “impossible”, or “humorous”. However, when simply considering them in terms of extensional logic, the novel concepts understood as a conjunctive concept will often lack meaning having an empty extension (consider “a tooth that is a chair”, “a pet flower”, etc.). Still, people use different strategies to produce new non-empty concepts: additive or integrative combination of features, alignment of features, instantiation, etc. All these strategies involve the ability to deal with conflicting attributes and the creation of new (combinations of) properties. We here consider in particular the case where a Head concept has superior ‘asymmetric’ control over steering the resulting concept combination (or hybridisation) with a Modifier concept. Specifically, we propose a dialogical approach to concept combination and discuss an implementation based on axiom weakening, which models the cognitive and logical mechanics of this asymmetric form of hybridisation
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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