1,721,028 research outputs found
An In-Memory XQuery/XPath Engine over a Compressed Structured Text Representation
Get PDFWe describe the architecture and main algorithmic design decisions for an XQuery/XPath processing engine over XML collections which will be represented using a self-indexing approach, that is, a compressed representation that will allow for basic searching and navigational operations in compressed form. The goal is a structure that occupies little space and thus permits manipulating large collections in main memory
An In-Memory XQuery/XPath Engine over a Compressed Structured Text Representation
Get PDFWe describe the architecture and main algorithmic design decisions for an XQuery/XPath processing engine over XML collections which will be represented using a self-indexing approach, that is, a compressed representation that will allow for basic searching and navigational operations in compressed form. The goal is a structure that occupies little space and thus permits manipulating large collections in main memory
Consistent RDF updates with correct dense deltas
Get PDFRDF is widely used in the Semantic Web for representing ontology data. Many real world RDF collections are large and contain complex graph relationships that represent knowledge in a particular domain. Such large RDF collections evolve in consequence of their representation of the changing world. Although this data may be distributed over the Internet, it needs to be managed and updated in the face of such evolutionary changes. In view of the size of typical collections, it is important to derive efficient ways of propagating updates to distributed data stores. The contribution of this paper is a detailed analysis of the performance of RDF change detection techniques. In addition the work describes a new approach to maintaining the consistency of RDF by using knowledge embedded in the structure to generate efficient update transactions. The evaluation of this approach indicates that it reduces the overall update size at the cost of increasing the processing time needed to generate the transactions
Virtual Network Mapping: A Graph Pattern Matching Approach
Get PDFVirtual network mapping (VNM) is to build a network on demand by deploying virtual machines in a substrate network, subject to constraints on capacity, bandwidth and latency. It is critical to data centers for coping with dynamic cloud workloads. This paper shows that VNM can be approached by graph pattern matching, a well-studied database topic. (1) We propose to model a virtual network request as a graph pattern carrying various constraints, and treat a substrate network as a graph in which nodes and edges bear attributes specifying their capacity. (2) We show that a variety of mapping requirements can be expressed in this model, such as virtual machine placement, network embedding and priority mapping. (3) In this model, we formulate VNM and its optimization problem with a mapping cost function. We establish complexity bounds of these problems for various mapping constraints, ranging from PTIME to NP-complete. For intractable optimization problems, we further show that these problems are approximation-hard, i.e., NPO-complete in general and APX-hard even for special cases
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
Definability problems for tree transducers
No full textIn dieser Arbeit betrachten wir Definierbarkeitsprobleme für ‘Tree Transducer’, das heißt
Maschinen, welche Bäume als Eingabe nehmen und diese zu Ausgabebäumen übersetzen.
Definierbarkeitsprobleme sind Fragen der folgenden Art: Ist es für einen gegebenen Tree
Transducer T aus einer Klasse C entscheidbar, ob es einen äquivalenten Tree Transducer aus der Klasse C ′ gibt und falls ja, können wir solch einen Tree Transducer konstruieren?
Falls die Antwort zu dieser Frage ‘ja’ ist, sagen wir, dass die Klasse C ′ innerhalb der
Klasse C definierbar ist. Typischerweise ist die Klasse C ′ eine strikte Unterklasse von C.
Im Speziellen liegt der Schwerpunkt in dieser Arbeit auf der Klasse der Top-Down Tree
Transducer und der Klasse der Attributed Tree Transducer
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
Machine learning classification of user attributes via eye movements
No full textThe advent of modern eye tracking devices has spawned a plethora of new research
on eye movements. Applications of these research results include the prediction of
diseases, of biometrics, of gender, or of cognitive developments in children. One par-
ticularly well studied topic is user identification. Another, less well studied one is
gender prediction. In this thesis, a common framework to predict users and gen-
der is proposed. Using this framework, we were able to improve the state-of-the-art
accuracies for both user identification and gender prediction. Further, unlike previ-
ous studies, the proposed approach was tested with different datasets consisting of
varying stimuli. We identify several factors that affect the identification accuracy.
Our main improvements in identification accuracy are due to three factors, select-
ing optimal hyper-parameters of the segmentation algorithm, adding higher-order
derivatives, and including blink information. For gender prediction, the thesis es-
tablishes several new insights. For instance, that gender prediction is possible for
prepubescent children aged 9–10. Previous research had suggested that significant
gender differences in eye movements can only be observed in adults. Various factors
are identified which affect the accuracy of gender prediction; for example, the length
of the gaze trajectory, possible fatigue of the participant (gender prediction works
better in the presence of fatigue), and the choice of feature ranking algorithms
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