1,721,018 research outputs found
Privacy-preserving and inconsistency-tolerant query answering in knowledge bases and databases
No full textIn recent decades, the widespread use of information systems has led to an increasing amount of sensitive data managed, posing several privacy and security risks. Controlled Query Evaluation (CQE) is a framework for limiting access to sensitive information when querying a system, while still providing useful responses. Initially proposed for databases, CQE has recently been studied for Description Logics ontologies, the logical formalization underpinning most Semantic Web technologies.
Central to CQE is the possibility of specifying a data protection policy in a declarative way, avoiding the need to actively alter data to ensure their security. The policy is enforced via optimal censors, which aim to minimally alter information while maintaining confidentiality. Notably, censors satisfying the so-called indistinguishability property also ensure that the end user is not even able to discern if the answers to a query have been altered or not.
The thesis investigates various CQE semantics based on the so-called optimal GA censors, which enjoy the indistinguishability property. In order not to arbitrarly pick a censor, we adopt the usual strategy of skeptical reasoning, i.e. answering according to all the optimal censors. Unfortunately, this approach is proven to be intractable, so we present an alternative semantics based on the intersection of all optimal GA censors (called IGA censor). Under this semantics, answering union of conjunctive queries (UCQs) in the Description Logic DL-LiteR is first-order (FO) rewritable, and thus in AC0 in data complexity.
Anyway, the intersection-based approach may cause losing too much information, which led us to explore smarter semantics for improving the throughput of query answers while preserving confidentiality. Towards this aim, we first show how to exploit a priority relation between ontology predicates for reducing the number of censors. Then, we consider the strategy of selecting censors dynamically, exploiting the order in which queries are posed for maximizing the cooperativity of the system. In both cases, we provide suitable FO rewriting techniques, proving that the nice computational properties of the IGA semantics are preserved.
The prioritized scenario also served as main setting for carrying out our experiments, wherein we implemented the newly-presented CQE techniques adapting them to the ontology-based data access methodology.
Moreover, the research extends to the related field of Consistent Query Answering (CQA), which studies how to handle inconsistencies when answering queries. Specifically, we consider knowledge bases in which a set of existential rules must always be satisfied by the underlying database. A central notion in CQA is the one of repair, that is a maximal subset of the database satisfying all the rules. As for query answering, similarly as done in CQE, we examine both skeptical reasoning and the intersection-based semantics, known as AR and IAR, respectively. We study a very expressive language of rules and identify many subclasses where repair checking and UCQ entailment are tractable, or even FO rewritable.
We finally investigate the integration between open and closed-world assumption, offering insights into utilizing open and closed predicates within the CQA framework, and provide the first set of complexity results for the aforenamed decision problems within this intriguing scenario
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Proceedings of the International Workshop on Semantic Technologies meet Recommender Systems & Big Data (SeRSy 2012@ISWC 2012)
No full textThese are the proceedings of the First Workshop on Semantic Technologies meet
Recommender Systems & Big Data (SeRSy 2012), held in conjunction with the 11th
International Semantic Web Conference (ISWC 2012).
People generally need more and more advanced tools that go beyond those
implementing the canonical search paradigm for seeking relevant information. A new search
paradigm is emerging, where the user perspective is completely reversed: from finding to
being found.
Recommender Systems may help to support this new perspective, because they have
the effect of pushing relevant objects, selected from a large space of possible options, to
potentially interested users. To achieve this result, recommendation techniques generally rely
on data referring to three kinds of objects: users, items and their relations. The widespread
success of Semantic Web techniques, creating a Web of interoperable and machine readable
data, can be also beneficial for recommender systems. Indeed, more and more semantic data
are published following the Linked Data principles, that enable to set up links between objects
in different data sources, by connecting information in a single global data space – the Web of
Data. Today, the Web of Data includes different types of knowledge represented in a
homogeneous form – sedimentary one (encyclopedic, cultural, linguistic, common-sense, ...)
and real-time one (news, data streams, ...). This data might be useful to interlink diverse
information about users, items, and their relations and implement reasoning mechanisms that
can support and improve the recommendation process.
The challenge is to investigate whether and how this large amount of wide-coverage
and linked semantic knowledge can significantly improve the search process in those tasks
that cannot be solved merely through a straightforward matching of queries and documents.
Such tasks involve finding information from large document collections, categorizing and
understanding that information, and producing some product, such as an actionable decision.
Examples of such tasks include understanding a health problem in order to make a medical
decision, or simply deciding which laptop to buy. Recommender systems support users
exactly in those complex tasks.
The primary goal of the workshop is to showcase cutting edge research in the
intersection of semantic technologies and recommender systems, by taking the best of the two
worlds. This combination may provide the Semantic Web community with important realworld
scenarios where its potential can be effectively exploited into systems performing
complex tasks.
We wish to thank all authors who submitted papers and all workshop participants for
fruitful discussions. We would like to thank the program committee members and external
referees for their timely expertise in carefully reviewing the submissions. We would also like
to thank our invited speaker Ora Lassila for his interesting and stimulating talk.
October 2012
The Workshop Chairs
Marco de Gemmis
Tommaso Di Noia
Pasquale Lops
Thomas Lukasiewicz
Giovanni Semerar
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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