A large number of ship locks in the Netherlands require renovation. This paper focuses on the app... more A large number of ship locks in the Netherlands require renovation. This paper focuses on the application of the synthesis-based engineering (SBE) in the design of supervisory controllers for ship locks, to achieve correct-by-construction control software. A configurator for SBE models for supervisor synthesis is proposed, based on parameters describing the mechanical composition. The accompanying tool, which supports model simulation, demonstrates improvement in time, quality and human error avoidance, and is already being used in the design of ship lock supervisors in Lelystad and Maasbracht. The tool was designed for ship locks but the structure of the tool allows adaptation for other families of systems.
Eleventh Annual Conference on Privacy, Security and Trust, 2013
Cultural heritage institutions and multimedia archives often delegate the task of annotating thei... more Cultural heritage institutions and multimedia archives often delegate the task of annotating their collections of artifacts to Web users. The use of crowdsourced annotations from the Web gives rise to trust issues. We propose an algorithm that, by making use of a combination of subjective logic, semantic relatedness measures and clustering, automates the process of evaluation for annotations represented by means of the Open Annotation ontology. The algorithm is evaluated over two different datasets coming from the cultural heritage domain.
Public authorities are increasingly sharing sets of open data.
These data are often preprocessed... more Public authorities are increasingly sharing sets of open data.
These data are often preprocessed (e.g. smoothened, aggregated) to avoid
to expose sensible data, while trying to preserve their reliability. We
present two procedures for tackling the lack of methods for measuring
the open data reliability. The first procedure is based on a comparison between open and closed data, and the second derives reliability estimates
from the analysis of open data only. We evaluate these two procedures
over data from the data.police.uk website and from the Hampshire Police Constabulary in the UK. With the first procedure we show that the
open data reliability is high despite preprocessing, while with the second
one we show how it is possible to achieve interesting results concerning
the open data reliability estimation when analyzing open data alone.
Diversity and profundity of the topics in cultural heritage
collections make experts from outsid... more Diversity and profundity of the topics in cultural heritage
collections make experts from outside the institution indispensable for
acquiring qualitative and comprehensive annotations. We define the concept of nichesourcing and present challenges in the process of obtaining qualitative annotations from people in these niches. We believe that
experts provide better annotations if this process is personalized. We
present a framework called Accurator, that allows to realize and
Communications in Computer and Information Science, 2014
Open Government Data often contain information that, in
more or less detail, regard private citi... more Open Government Data often contain information that, in
more or less detail, regard private citizens. For this reason, before publishing
them, public authorities manipulate data to remove any sensitive
information while trying to preserve their reliability. This paper addresses
the lack of tools aimed at measuring the reliability of these data. We
present two procedures for the assessment of the Open Government Data
reliability, one based on a comparison between open and closed data, and
the other based on analysis of open data only.We evaluate the procedures
over data from the data.police.uk website and from the Hampshire Police
Constabulary in the United Kingdom. The procedures effectively allow
estimating the reliability of open data and, actually, their reliability is
high even though they are aggregated and smoothed.
We prove the correctness of a sliding window protocol with an arbitrary finite window size n and ... more We prove the correctness of a sliding window protocol with an arbitrary finite window size n and sequence numbers modulo 2n. The correctness consists of showing that the sliding window protocol is branching bisimilar to a queue of capacity 2n. The proof is given entirely on the basis of an axiomatic theory.
We prove the correctness of a sliding window protocol with an arbitrary finite window size n and ... more We prove the correctness of a sliding window protocol with an arbitrary finite window size n and sequence numbers modulo 2n. The correctness consists of showing that the sliding window protocol is branching bisimilar to a queue of capacity 2n. The proof is given entirely on the basis of an axiomatic theory, and has been checked in the theorem prover PVS. .nl a window. When an acknowledgment reaches the sender, indicating that k messages have arrived correctly, the window slides forward, so that the sending buffer can contain messages with sequence numbers i + k to i + k + n (modulo 2n). The window of the receiver slides forward when the first element in this window is passed on to the environment.
Pushdown automata may contain transitions that are never used in any accepting run
of the automa... more Pushdown automata may contain transitions that are never used in any accepting run
of the automaton. We present an algorithm for detecting such useless transitions. A
finite automaton that captures the possible stack content during runs of the pushdown
automaton, is first constructed in a forward procedure to determine which transitions
are reachable, and then employed in a backward procedure to determine which of these
transitions can lead to a final state. An implementation of the algorithm is shown to
exhibit a favorable performance.
In model checking, abstractions can cause spurious results, which need to be verified in the conc... more In model checking, abstractions can cause spurious results, which need to be verified in the concrete system to gain conclusive results. Verification based on multi-valued model checking can distinguish conclusive and inconclusive results, while increasing precision over traditional two-valued over- and under-abstractions. This paper describes the
theory and implementation of multi-valued model checking for Promela specifications. We believe our tool Bonsai is the first four-valued model checker capable of multi-valued verification of parallel models, i.e. consisting of multiple concurrent processes. A novel aspect is the ability to only partially abstract a model, keeping parts of it concrete.
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
Web data often manifest high levels of uncertainty. We focus on categorical Web data and we repre... more Web data often manifest high levels of uncertainty. We focus on categorical Web data and we represent these uncertainty levels as first- or second-order uncertainty. By means of concrete examples, we show how to quantify and handle these uncertainties using the BetaBinomial and the Dirichlet-Multinomial models, as well as how take into account possibly unseen categories in our samples by using the Dirichlet process. We conclude by exemplifying how these higher-order models can be used as a basis for analyzing datasets, once at least part of their uncertainty has been taken into account. We demonstrate how to use the Battacharyya stastistical distance to quantify the similarity between Dirichlet distributions, and use such results to analyze a Web dataset of piracy attacks both visually and automatically
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
In many systems, the determination of trust is reduced to reputation estimation. However, reputat... more In many systems, the determination of trust is reduced to reputation estimation. However, reputation is just one way of determining trust. The estimation of trust can be tackled from a variety of other perspectives. In this chapter, we model trust relying on user reputation, user demographics and from provenance. We then explore the effects of combining trust computed through these different methods. Concretely, the first contribution of this chapter is a study of the correlations of demographics with trust. This study helps us to understand which categories of users are better candidates for annotation tasks in the cultural heritage domain. Secondly, we detail a procedure for computing reputation-based trust assessments. The user reputation is modeled in subjective logic based on the user’s performance in the system evaluated (Waisda? in the case of the work presented here). The third contribution is a procedure for computing trust values based on provenance information, represented using the W3C PROV model. We show how merging the results of these procedures can be beneficial for the reliability of the estimated trust value. We evaluate the proposed procedures and their merger by estimating and verifying the trustworthiness of the
tags created within the Waisda? video tagging game from the Netherlands Institute for Sound and Vision. Through a quantitative analysis of the results, we demonstrate that using provenance and demographic information is beneficial for the accuracy of trust assessments.
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
Subjective logic is a powerful probabilistic logic which is useful to handle data in case of unce... more Subjective logic is a powerful probabilistic logic which is useful to handle data in case of uncertainty. Subjective logic and the Semantic Web can mutually benefit from each other, since subjective logic is useful to handle the inner noisiness of the Semantic Web data, while the Semantic Web offers a means to obtain evidence useful for performing evidential reasoning based on subjective logic. In this chapter we describe three extensions and applications of subjective logic in the Semantic Web, namely: the use of deterministic and probabilistic semantic similarity measures for weighing subjective opinions, a way for accounting for partial observations, and “open world opinion”, i.e. subjective opinions based on Dirichlet processes, which extend multinomial opinions. For each of these extensions, we provide examples and applications to prove their validity.
Cultural heritage institutions are employing crowdsourcing techniques to enrich their collection.... more Cultural heritage institutions are employing crowdsourcing techniques to enrich their collection. However, assessing the quality of crowdsourced annotations is a challenge for these institutions and manually evaluating all annotations is not feasible. We employ Support Vector Machines and feature set selectors to understand which annotator and
annotation properties are relevant to the annotation quality. In addition we propose a trust model to build an annotator reputation using subjective logic and assess the relevance of both annotator and annotation properties on the reputation. We applied our models to the Steve.museum dataset and found that a subset of annotation properties can identify useful annotations with a precision of 90%. However, our studied annotator properties were less predictive.
We formally verify that TCP satisfies its requirements when extended with the Window Scale Option... more We formally verify that TCP satisfies its requirements when extended with the Window Scale Option. With the aid of our μCRL specification and the LTSmin toolset, we verify that our specification of unidirectional TCP Data Transfer extended with the Window Scale Option does not deadlock, and that its external behaviour is branching bisimilar to a FIFO queue for a significantly large instance. Separately, we verify that a connection may only be closed if both entities accept the CLOSE call from the Application Layer. Finally, we recommend a rewording of the specification regarding how a zero window is probed, ensuring deadlocks do not arise as a result of misinterpretation.
A comprehensive guide to distributed algorithms that emphasizes examples and exercises rather tha... more A comprehensive guide to distributed algorithms that emphasizes examples and exercises rather than mathematical argumentation.
This book offers students and researchers a guide to distributed algorithms that emphasizes examples and exercises rather than the intricacies of mathematical models. It avoids mathematical argumentation, often a stumbling block for students, teaching algorithmic thought rather than proofs and logic. This approach allows the student to learn a large number of algorithms within a relatively short span of time. Algorithms are explained through brief, informal descriptions, illuminating examples, and practical exercises. The examples and exercises allow readers to understand algorithms intuitively and from different perspectives. Proof sketches, arguing the correctness of an algorithm or explaining the idea behind fundamental results, are also included. An appendix offers pseudocode descriptions of many algorithms.
Distributed algorithms are performed by a collection of computers that send messages to each other or by multiple software threads that use the same shared memory. The algorithms presented in the book are for the most part classics, selected because they shed light on the algorithmic design of distributed systems or on key issues in distributed computing and concurrent programming.
Distributed Algorithms can be used in courses for upper-level undergraduates or graduate students in computer science, or as a reference for researchers in the field.
A large number of ship locks in the Netherlands require renovation. This paper focuses on the app... more A large number of ship locks in the Netherlands require renovation. This paper focuses on the application of the synthesis-based engineering (SBE) in the design of supervisory controllers for ship locks, to achieve correct-by-construction control software. A configurator for SBE models for supervisor synthesis is proposed, based on parameters describing the mechanical composition. The accompanying tool, which supports model simulation, demonstrates improvement in time, quality and human error avoidance, and is already being used in the design of ship lock supervisors in Lelystad and Maasbracht. The tool was designed for ship locks but the structure of the tool allows adaptation for other families of systems.
Eleventh Annual Conference on Privacy, Security and Trust, 2013
Cultural heritage institutions and multimedia archives often delegate the task of annotating thei... more Cultural heritage institutions and multimedia archives often delegate the task of annotating their collections of artifacts to Web users. The use of crowdsourced annotations from the Web gives rise to trust issues. We propose an algorithm that, by making use of a combination of subjective logic, semantic relatedness measures and clustering, automates the process of evaluation for annotations represented by means of the Open Annotation ontology. The algorithm is evaluated over two different datasets coming from the cultural heritage domain.
Public authorities are increasingly sharing sets of open data.
These data are often preprocessed... more Public authorities are increasingly sharing sets of open data.
These data are often preprocessed (e.g. smoothened, aggregated) to avoid
to expose sensible data, while trying to preserve their reliability. We
present two procedures for tackling the lack of methods for measuring
the open data reliability. The first procedure is based on a comparison between open and closed data, and the second derives reliability estimates
from the analysis of open data only. We evaluate these two procedures
over data from the data.police.uk website and from the Hampshire Police Constabulary in the UK. With the first procedure we show that the
open data reliability is high despite preprocessing, while with the second
one we show how it is possible to achieve interesting results concerning
the open data reliability estimation when analyzing open data alone.
Diversity and profundity of the topics in cultural heritage
collections make experts from outsid... more Diversity and profundity of the topics in cultural heritage
collections make experts from outside the institution indispensable for
acquiring qualitative and comprehensive annotations. We define the concept of nichesourcing and present challenges in the process of obtaining qualitative annotations from people in these niches. We believe that
experts provide better annotations if this process is personalized. We
present a framework called Accurator, that allows to realize and
Communications in Computer and Information Science, 2014
Open Government Data often contain information that, in
more or less detail, regard private citi... more Open Government Data often contain information that, in
more or less detail, regard private citizens. For this reason, before publishing
them, public authorities manipulate data to remove any sensitive
information while trying to preserve their reliability. This paper addresses
the lack of tools aimed at measuring the reliability of these data. We
present two procedures for the assessment of the Open Government Data
reliability, one based on a comparison between open and closed data, and
the other based on analysis of open data only.We evaluate the procedures
over data from the data.police.uk website and from the Hampshire Police
Constabulary in the United Kingdom. The procedures effectively allow
estimating the reliability of open data and, actually, their reliability is
high even though they are aggregated and smoothed.
We prove the correctness of a sliding window protocol with an arbitrary finite window size n and ... more We prove the correctness of a sliding window protocol with an arbitrary finite window size n and sequence numbers modulo 2n. The correctness consists of showing that the sliding window protocol is branching bisimilar to a queue of capacity 2n. The proof is given entirely on the basis of an axiomatic theory.
We prove the correctness of a sliding window protocol with an arbitrary finite window size n and ... more We prove the correctness of a sliding window protocol with an arbitrary finite window size n and sequence numbers modulo 2n. The correctness consists of showing that the sliding window protocol is branching bisimilar to a queue of capacity 2n. The proof is given entirely on the basis of an axiomatic theory, and has been checked in the theorem prover PVS. .nl a window. When an acknowledgment reaches the sender, indicating that k messages have arrived correctly, the window slides forward, so that the sending buffer can contain messages with sequence numbers i + k to i + k + n (modulo 2n). The window of the receiver slides forward when the first element in this window is passed on to the environment.
Pushdown automata may contain transitions that are never used in any accepting run
of the automa... more Pushdown automata may contain transitions that are never used in any accepting run
of the automaton. We present an algorithm for detecting such useless transitions. A
finite automaton that captures the possible stack content during runs of the pushdown
automaton, is first constructed in a forward procedure to determine which transitions
are reachable, and then employed in a backward procedure to determine which of these
transitions can lead to a final state. An implementation of the algorithm is shown to
exhibit a favorable performance.
In model checking, abstractions can cause spurious results, which need to be verified in the conc... more In model checking, abstractions can cause spurious results, which need to be verified in the concrete system to gain conclusive results. Verification based on multi-valued model checking can distinguish conclusive and inconclusive results, while increasing precision over traditional two-valued over- and under-abstractions. This paper describes the
theory and implementation of multi-valued model checking for Promela specifications. We believe our tool Bonsai is the first four-valued model checker capable of multi-valued verification of parallel models, i.e. consisting of multiple concurrent processes. A novel aspect is the ability to only partially abstract a model, keeping parts of it concrete.
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
Web data often manifest high levels of uncertainty. We focus on categorical Web data and we repre... more Web data often manifest high levels of uncertainty. We focus on categorical Web data and we represent these uncertainty levels as first- or second-order uncertainty. By means of concrete examples, we show how to quantify and handle these uncertainties using the BetaBinomial and the Dirichlet-Multinomial models, as well as how take into account possibly unseen categories in our samples by using the Dirichlet process. We conclude by exemplifying how these higher-order models can be used as a basis for analyzing datasets, once at least part of their uncertainty has been taken into account. We demonstrate how to use the Battacharyya stastistical distance to quantify the similarity between Dirichlet distributions, and use such results to analyze a Web dataset of piracy attacks both visually and automatically
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
In many systems, the determination of trust is reduced to reputation estimation. However, reputat... more In many systems, the determination of trust is reduced to reputation estimation. However, reputation is just one way of determining trust. The estimation of trust can be tackled from a variety of other perspectives. In this chapter, we model trust relying on user reputation, user demographics and from provenance. We then explore the effects of combining trust computed through these different methods. Concretely, the first contribution of this chapter is a study of the correlations of demographics with trust. This study helps us to understand which categories of users are better candidates for annotation tasks in the cultural heritage domain. Secondly, we detail a procedure for computing reputation-based trust assessments. The user reputation is modeled in subjective logic based on the user’s performance in the system evaluated (Waisda? in the case of the work presented here). The third contribution is a procedure for computing trust values based on provenance information, represented using the W3C PROV model. We show how merging the results of these procedures can be beneficial for the reliability of the estimated trust value. We evaluate the proposed procedures and their merger by estimating and verifying the trustworthiness of the
tags created within the Waisda? video tagging game from the Netherlands Institute for Sound and Vision. Through a quantitative analysis of the results, we demonstrate that using provenance and demographic information is beneficial for the accuracy of trust assessments.
Uncertainty Reasoning for the Semantic Web III - Revised Selected Papers of URSW 2011-2013, 2014
Subjective logic is a powerful probabilistic logic which is useful to handle data in case of unce... more Subjective logic is a powerful probabilistic logic which is useful to handle data in case of uncertainty. Subjective logic and the Semantic Web can mutually benefit from each other, since subjective logic is useful to handle the inner noisiness of the Semantic Web data, while the Semantic Web offers a means to obtain evidence useful for performing evidential reasoning based on subjective logic. In this chapter we describe three extensions and applications of subjective logic in the Semantic Web, namely: the use of deterministic and probabilistic semantic similarity measures for weighing subjective opinions, a way for accounting for partial observations, and “open world opinion”, i.e. subjective opinions based on Dirichlet processes, which extend multinomial opinions. For each of these extensions, we provide examples and applications to prove their validity.
Cultural heritage institutions are employing crowdsourcing techniques to enrich their collection.... more Cultural heritage institutions are employing crowdsourcing techniques to enrich their collection. However, assessing the quality of crowdsourced annotations is a challenge for these institutions and manually evaluating all annotations is not feasible. We employ Support Vector Machines and feature set selectors to understand which annotator and
annotation properties are relevant to the annotation quality. In addition we propose a trust model to build an annotator reputation using subjective logic and assess the relevance of both annotator and annotation properties on the reputation. We applied our models to the Steve.museum dataset and found that a subset of annotation properties can identify useful annotations with a precision of 90%. However, our studied annotator properties were less predictive.
We formally verify that TCP satisfies its requirements when extended with the Window Scale Option... more We formally verify that TCP satisfies its requirements when extended with the Window Scale Option. With the aid of our μCRL specification and the LTSmin toolset, we verify that our specification of unidirectional TCP Data Transfer extended with the Window Scale Option does not deadlock, and that its external behaviour is branching bisimilar to a FIFO queue for a significantly large instance. Separately, we verify that a connection may only be closed if both entities accept the CLOSE call from the Application Layer. Finally, we recommend a rewording of the specification regarding how a zero window is probed, ensuring deadlocks do not arise as a result of misinterpretation.
A comprehensive guide to distributed algorithms that emphasizes examples and exercises rather tha... more A comprehensive guide to distributed algorithms that emphasizes examples and exercises rather than mathematical argumentation.
This book offers students and researchers a guide to distributed algorithms that emphasizes examples and exercises rather than the intricacies of mathematical models. It avoids mathematical argumentation, often a stumbling block for students, teaching algorithmic thought rather than proofs and logic. This approach allows the student to learn a large number of algorithms within a relatively short span of time. Algorithms are explained through brief, informal descriptions, illuminating examples, and practical exercises. The examples and exercises allow readers to understand algorithms intuitively and from different perspectives. Proof sketches, arguing the correctness of an algorithm or explaining the idea behind fundamental results, are also included. An appendix offers pseudocode descriptions of many algorithms.
Distributed algorithms are performed by a collection of computers that send messages to each other or by multiple software threads that use the same shared memory. The algorithms presented in the book are for the most part classics, selected because they shed light on the algorithmic design of distributed systems or on key issues in distributed computing and concurrent programming.
Distributed Algorithms can be used in courses for upper-level undergraduates or graduate students in computer science, or as a reference for researchers in the field.
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Papers by Wan Fokkink
These data are often preprocessed (e.g. smoothened, aggregated) to avoid
to expose sensible data, while trying to preserve their reliability. We
present two procedures for tackling the lack of methods for measuring
the open data reliability. The first procedure is based on a comparison between open and closed data, and the second derives reliability estimates
from the analysis of open data only. We evaluate these two procedures
over data from the data.police.uk website and from the Hampshire Police Constabulary in the UK. With the first procedure we show that the
open data reliability is high despite preprocessing, while with the second
one we show how it is possible to achieve interesting results concerning
the open data reliability estimation when analyzing open data alone.
collections make experts from outside the institution indispensable for
acquiring qualitative and comprehensive annotations. We define the concept of nichesourcing and present challenges in the process of obtaining qualitative annotations from people in these niches. We believe that
experts provide better annotations if this process is personalized. We
present a framework called Accurator, that allows to realize and
more or less detail, regard private citizens. For this reason, before publishing
them, public authorities manipulate data to remove any sensitive
information while trying to preserve their reliability. This paper addresses
the lack of tools aimed at measuring the reliability of these data. We
present two procedures for the assessment of the Open Government Data
reliability, one based on a comparison between open and closed data, and
the other based on analysis of open data only.We evaluate the procedures
over data from the data.police.uk website and from the Hampshire Police
Constabulary in the United Kingdom. The procedures effectively allow
estimating the reliability of open data and, actually, their reliability is
high even though they are aggregated and smoothed.
of the automaton. We present an algorithm for detecting such useless transitions. A
finite automaton that captures the possible stack content during runs of the pushdown
automaton, is first constructed in a forward procedure to determine which transitions
are reachable, and then employed in a backward procedure to determine which of these
transitions can lead to a final state. An implementation of the algorithm is shown to
exhibit a favorable performance.
theory and implementation of multi-valued model checking for Promela specifications. We believe our tool Bonsai is the first four-valued model checker capable of multi-valued verification of parallel models, i.e. consisting of multiple concurrent processes. A novel aspect is the ability to only partially abstract a model, keeping parts of it concrete.
tags created within the Waisda? video tagging game from the Netherlands Institute for Sound and Vision. Through a quantitative analysis of the results, we demonstrate that using provenance and demographic information is beneficial for the accuracy of trust assessments.
annotation properties are relevant to the annotation quality. In addition we propose a trust model to build an annotator reputation using subjective logic and assess the relevance of both annotator and annotation properties on the reputation. We applied our models to the Steve.museum dataset and found that a subset of annotation properties can identify useful annotations with a precision of 90%. However, our studied annotator properties were less predictive.
This book offers students and researchers a guide to distributed algorithms that emphasizes examples and exercises rather than the intricacies of mathematical models. It avoids mathematical argumentation, often a stumbling block for students, teaching algorithmic thought rather than proofs and logic. This approach allows the student to learn a large number of algorithms within a relatively short span of time. Algorithms are explained through brief, informal descriptions, illuminating examples, and practical exercises. The examples and exercises allow readers to understand algorithms intuitively and from different perspectives. Proof sketches, arguing the correctness of an algorithm or explaining the idea behind fundamental results, are also included. An appendix offers pseudocode descriptions of many algorithms.
Distributed algorithms are performed by a collection of computers that send messages to each other or by multiple software threads that use the same shared memory. The algorithms presented in the book are for the most part classics, selected because they shed light on the algorithmic design of distributed systems or on key issues in distributed computing and concurrent programming.
Distributed Algorithms can be used in courses for upper-level undergraduates or graduate students in computer science, or as a reference for researchers in the field.
These data are often preprocessed (e.g. smoothened, aggregated) to avoid
to expose sensible data, while trying to preserve their reliability. We
present two procedures for tackling the lack of methods for measuring
the open data reliability. The first procedure is based on a comparison between open and closed data, and the second derives reliability estimates
from the analysis of open data only. We evaluate these two procedures
over data from the data.police.uk website and from the Hampshire Police Constabulary in the UK. With the first procedure we show that the
open data reliability is high despite preprocessing, while with the second
one we show how it is possible to achieve interesting results concerning
the open data reliability estimation when analyzing open data alone.
collections make experts from outside the institution indispensable for
acquiring qualitative and comprehensive annotations. We define the concept of nichesourcing and present challenges in the process of obtaining qualitative annotations from people in these niches. We believe that
experts provide better annotations if this process is personalized. We
present a framework called Accurator, that allows to realize and
more or less detail, regard private citizens. For this reason, before publishing
them, public authorities manipulate data to remove any sensitive
information while trying to preserve their reliability. This paper addresses
the lack of tools aimed at measuring the reliability of these data. We
present two procedures for the assessment of the Open Government Data
reliability, one based on a comparison between open and closed data, and
the other based on analysis of open data only.We evaluate the procedures
over data from the data.police.uk website and from the Hampshire Police
Constabulary in the United Kingdom. The procedures effectively allow
estimating the reliability of open data and, actually, their reliability is
high even though they are aggregated and smoothed.
of the automaton. We present an algorithm for detecting such useless transitions. A
finite automaton that captures the possible stack content during runs of the pushdown
automaton, is first constructed in a forward procedure to determine which transitions
are reachable, and then employed in a backward procedure to determine which of these
transitions can lead to a final state. An implementation of the algorithm is shown to
exhibit a favorable performance.
theory and implementation of multi-valued model checking for Promela specifications. We believe our tool Bonsai is the first four-valued model checker capable of multi-valued verification of parallel models, i.e. consisting of multiple concurrent processes. A novel aspect is the ability to only partially abstract a model, keeping parts of it concrete.
tags created within the Waisda? video tagging game from the Netherlands Institute for Sound and Vision. Through a quantitative analysis of the results, we demonstrate that using provenance and demographic information is beneficial for the accuracy of trust assessments.
annotation properties are relevant to the annotation quality. In addition we propose a trust model to build an annotator reputation using subjective logic and assess the relevance of both annotator and annotation properties on the reputation. We applied our models to the Steve.museum dataset and found that a subset of annotation properties can identify useful annotations with a precision of 90%. However, our studied annotator properties were less predictive.
This book offers students and researchers a guide to distributed algorithms that emphasizes examples and exercises rather than the intricacies of mathematical models. It avoids mathematical argumentation, often a stumbling block for students, teaching algorithmic thought rather than proofs and logic. This approach allows the student to learn a large number of algorithms within a relatively short span of time. Algorithms are explained through brief, informal descriptions, illuminating examples, and practical exercises. The examples and exercises allow readers to understand algorithms intuitively and from different perspectives. Proof sketches, arguing the correctness of an algorithm or explaining the idea behind fundamental results, are also included. An appendix offers pseudocode descriptions of many algorithms.
Distributed algorithms are performed by a collection of computers that send messages to each other or by multiple software threads that use the same shared memory. The algorithms presented in the book are for the most part classics, selected because they shed light on the algorithmic design of distributed systems or on key issues in distributed computing and concurrent programming.
Distributed Algorithms can be used in courses for upper-level undergraduates or graduate students in computer science, or as a reference for researchers in the field.