1,720,986 research outputs found
Adaptive Reshaping of Web of Things and mobile software for the Fog Computing Era
Get PDFThe software has become an essential part of every aspect of the society and our daily life. This is indicated by many recent trends in our society
– healthcare, smart homes, smart cities, (autonomous) robots, autonomous connected vehicles and so on – all contain an ever-increasing amount of software.
These trends also indicate that the single device computing era is coming to an end. However, the development and software architectures have
not changed much during past ten years. At the moment, Cloud-based services are the de facto way how the software is constructed, and then provided
for the end users in the form of Web and native apps. Moreover, from a software architecture point of view, Internet of Things (IoT) poses many
interesting challenges due to its unpredictable yet adaptive requirements.
In this thesis, we investigate challenges related to Web of Things (WoT) and mobile software in the Fog Computing era in order to improve their adaptive
behaviour
Simulation based formal verification of cyber-physical systems
Get PDFCyber-Physical Systems (CPSs) have become an intrinsic part of the 21st century world. Systems like Smart Grids, Transportation, and Healthcare help us run our lives and businesses smoothly, successfully and safely. Since malfunctions in these CPSs can have serious, expensive, sometimes fatal consequences, System-Level Formal Verification (SLFV) tools are vital to minimise the likelihood of errors occurring during the development process and beyond. Their applicability is supported by the increasingly widespread use of Model Based Design (MBD) tools. MBD enables the simulation of CPS models in order to check for their correct behaviour from the very initial design phase. The disadvantage is that SLFV for complex CPSs is an extremely time-consuming process, which typically requires several months of simulation. Current SLFV tools are aimed at accelerating the verification process with multiple simulators working simultaneously. To this end, they compute all the scenarios in advance in such a way as to split and simulate them in parallel. Furthermore, they compute optimised simulation campaigns in order to simulate common prefixes of these scenarios only once, thus avoiding redundant simulation. Nevertheless, there are still limitations that prevent a more widespread adoption of SLFV tools. Firstly, current tools cannot optimise simulation campaigns from existing datasets with collected scenarios. Secondly, there are currently no methods to predict the time required to complete the SLFV process. This lack of ability to predict the length of the process makes scheduling verification activities highly problematic. In this thesis, we present how we are able to overcome these limitations with the use of a simulation campaign optimiser and an execution time estimator. The optimiser tool is aimed at speeding up the SLFV process by using a data-intensive algorithm to obtain optimised simulation campaigns from existing datasets, that may contain a large quantity of collected scenarios. The estimator tool is able to accurately predict the execution time to simulate a given simulation campaign by using an effective machine-independent method
Self-Repairing systems modeling and verification using AGG
No full textSelf-Repairing (or healing) systems are systems
equipped with a mechanism that monitors the system behaviour
to determine whether it behaves within prefixed parameters.
If a deviation exists, then the system itself is in charge of
adapting its configuration. In this paper we show how to model
self-repairing systems by means of Dynamic Software Architectures (DSAs). DSAs are formalized as Typed (hyper) Graph Grammars (TGGs) and this formalization enables verification of correctness and completeness of self-repairing systems. DSAs are modeled and verified by using the Attributed Graph Grammar system (AGG). The overall approach is applied to a traffic light system case study
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
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
Formal Analysis and Verification of Self-Healing Systems
No full textSelf-healing (SH) systems are characterized by an automatic
discovery of system failures, and techniques how to recover from these situations. In this paper, we show how to model SH systems using algebraic graph transformation. These systems are modeled as typed graph grammars enriched with graph constraints. This allows not only for formal modelling of consistency and operational properties, but also for their formalanalysis and verication using the tool AGG. As main results, we present sufficient static conditions for self-healing properties, deadlock freeness and liveness of SH-systems. The overall approach is applied to a traffic light system case study, where the corresponding properties are verified
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