31 research outputs found
Assuming Data Integrity and Empirical Evidence to The Contrary
Background: Not all respondents to surveys apply their minds or understand
the posed questions, and as such provide answers which lack coherence, and
this threatens the integrity of the research. Casual inspection and limited
research of the 10-item Big Five Inventory (BFI-10), included in the dataset of
the World Values Survey (WVS), suggested that random responses may be
common.
Objective: To specify the percentage of cases in the BRI-10 which include
incoherent or contradictory responses and to test the extent to which the
removal of these cases will improve the quality of the dataset.
Method: The WVS data on the BFI-10, measuring the Big Five Personality (B5P), in South Africa (N=3 531), was used. Incoherent or contradictory responses were removed. Then the cases from the cleaned-up dataset were analysed for their theoretical validity.
Results: Only 1 612 (45.7%) cases were identified as not including incoherent
or contradictory responses. The cleaned-up data did not mirror the B5P- structure, as was envisaged. The test for common method bias was negative. Conclusion: In most cases the responses were incoherent. Cleaning up the data did not improve the psychometric properties of the BFI-10. This raises concerns about the quality of the WVS data, the BFI-10, and the universality of B5P-theory. Given these results, it would be unwise to use the BFI-10 in South Africa. Researchers are alerted to do a proper assessment of the
psychometric properties of instruments before they use it, particularly in a
cross-cultural setting
Leading Towards Voice and Innovation: The Role of Psychological Contract
Background: Empirical evidence generally suggests that psychological
contract breach (PCB) leads to negative outcomes. However, some literature
argues that, occasionally, PCB leads to positive outcomes.
Aim: To empirically determine when these positive outcomes occur, focusing
on the role of psychological contract (PC) and leadership style (LS), and
outcomes such as employ voice (EV) and innovative work behaviour (IWB).
Method: A cross-sectional survey design was adopted, using reputable
questionnaires on PC, PCB, EV, IWB, and leadership styles. Correlation
analyses were used to test direct links within the model, while regression
analyses were used to test for the moderation effects.
Results: Data with acceptable psychometric properties were collected from 11
organisations (N=620). The results revealed that PCB does not lead to
substantial changes in IWB. PCB correlated positively with prohibitive EV, but did not influence promotive EV, which was a significant driver of IWB. Leadership styles were weak predictors of EV and IWB, and LS only partially moderated the PCB-EV relationship. Conclusion: PCB did not lead to positive outcomes. Neither did LS influencing the relationships between PCB and EV or IWB. Further, LS only partially influenced the relationships between variables, and not in a manner which positively influence IWB
Exogenous Coordination of Concurrent Software Components with JavaBIP
A strong separation of concerns is necessary in order to make the design of domain-specific functional components independent from cross-cutting concerns, such as concurrent access to the shared resources of the execution platform. Native coordination mechanisms, such as locks and monitors, allow developers to address these issues. However, such solutions are not modular, they are complex to design, debug and maintain. We present the JavaBIP framework that allows developers to think on a higher level of abstraction and clearly separate the functional and coordination aspects of the system behavior. It implements the principles of the BIP component framework rooted in rigorous operational semantics. It allows the coordination of existing concurrent software components in an exogenous manner, relying exclusively on annotations, component APIs and external specification files. We introduce the annotation and specification syntax of JavaBIP and illustrate its use on realistic examples; present the architecture of our implementation, which is modular and easily extensible; provide and discuss performance evaluation results
DSpace 5.x Documentation
DSpace is an open source software platform that enables organisations to:
- capture and describe digital material using a submission workflow module, or a variety of programmatic ingest options
- distribute an organisation's digital assets over the web through a search and retrieval system
- preserve digital assets over the long term
This system documentation includes a functional overview of the system, which is a good introduction to the
capabilities of the system, and should be readable by non-technical folk. Everyone should read this section first
because it introduces some terminology used throughout the rest of the documentation.
For people actually running a DSpace service, there is an installation guide, and sections on configuration and
the directory structure.
Finally, for those interested in the details of how DSpace works, and those potentially interested in modifying the
code for their own purposes, there is a detailed architecture and design section.DSpace is an open source software platform that enables organisations to:
- capture and describe digital material using a submission workflow module, or a variety of programmatic ingest options
- distribute an organisation's digital assets over the web through a search and retrieval system
- preserve digital assets over the long term
This system documentation includes a functional overview of the system, which is a good introduction to the
capabilities of the system, and should be readable by non-technical folk. Everyone should read this section first
because it introduces some terminology used throughout the rest of the documentation.
For people actually running a DSpace service, there is an installation guide, and sections on configuration and
the directory structure.
Finally, for those interested in the details of how DSpace works, and those potentially interested in modifying the
code for their own purposes, there is a detailed architecture and design section
Modelling Architecture Styles
Software systems tend to increase over time in size and complexity. Their development usually spans a long period of time and often results in systems that are hard to understand, debug and maintain. Architectures are common means for organising coordination between components in order to build complex systems and make them manageable. They allow thinking on a higher plane and avoiding low-level mistakes. Grouping architectures that share common characteristics into architecture styles assists component re-use and thus, the cost-effective development of systems. Additionally, architecture styles provide means for ensuring correctness-by-construction by enforcing global properties. The main goal of this thesis is to propose and study formalisms for modelling architectures and architecture styles. For the specification of architectures, we study interaction logics, which are Boolean algebras on a set of component actions. We study a modelling methodology based on first-order interaction logic for writing architecture constraints. To validate the applicability of the approach, we developed the JavaBIP framework that integrates architectures into mainstream software development. JavaBIP receives as input architecture specifications, which it then uses to coordinate software components without requiring access to their source code. JavaBIP implements the principles of the BIP component framework. For the specification of architecture styles, we propose configuration logics, which are powerset extensions of interaction logic. Propositional configuration logic formulas are generated from formulas of interaction logic by using the operators union, intersection and complementation, as well as a coalescing operator. We provide a complete axiomatisation of the propositional configuration logic and a decision procedure for checking that an architecture satisfies given logical specifications. To allow genericity of specifications, we study higher-order extensions of the propositional configuration logic. We provide several examples illustrating the application of configuration logics to the characterisation of architecture styles. For the specification of architecture styles, we also propose architecture diagrams, which is a graphical language rooted in rigorous semantics. We provide methods to assist software developers to specify consistent architecture diagrams, generate the conforming architectures of a style and check whether an architecture model meets given style requirements. We present a full encoding of architecture diagrams into configuration logics. Finally, we report on applications of architecture diagrams to modelling architecture styles identified in realistic case studies of on-board satellite software
Aspect oriented service composition for telecommunication applications
This PhD dissertation investigates how to overcome the negative effects of cross cutting concerns in the development of composite service applications. It proposes a combination of dynamic aspect oriented programming with a rules driven service composition mechanism. This combination allows very flexible utilization of aspects based on run-time data. The thesis contributes a join-point model and it integrates techniques for weaving and advice definition into the underlying composition language and execution engine. A particular focus of the thesis is telecommunication applications with their unique model for utilizing heterogeneous constituent services and their severe real-time requirements. Next to its primary use for modular implementation and flexible deployment of concerns in telecommunication applications, the dissertation discusses AOP as a feature for automated management and customization of service applications. The verification of the proposed solution contributes a detailed assessment of run-time performance, including a theoretical model of the AOP implementation. It allows predicting the performance of various alternative solutions. The proposed solution for combined AOP and service composition provides properties, which directly address challenges in pervasive computing and the Internet of things. Thus, this dissertation advances beyond the telecommunication domain with results applicable to various highly relevant technical developments
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On SIP Server Clusters and the Migration to Cloud Computing Platforms
This thesis looks in depth at telephony server clusters, the modern switchboards at the core of a packet-based telephony service. The most widely used de facto standard protocols for telecommunications are the Session Initiation Protocol (SIP) and the Real Time Protocol (RTP). SIP is a signaling protocol used to establish, maintain, and tear down communication channel between two or more parties. RTP is a media delivery protocol that allows packets to carry digitized voice, video, or text.
SIP telephony server clusters that provide communications services, such as an emergency calling service, must be scalable and highly available. We evaluate existing commercial and open source telephony server clusters to see how they differ in scalability and high availability.
We also investigate how a scalable SIP server cluster can be built on a cloud computing platform. Elasticity of resources is an attractive property for SIP server clusters because it allows the cluster to grow or shrink organically based on traffic load. However, simply deploying existing clusters to cloud computing platforms is not good enough to take full advantage of elasticity. We explore the design and implementation of clusters that scale in real-time. The database tier of our cluster was modified to use a scalable key-value store so that both the SIP proxy tier and the database tier can scale separately. Load monitoring and reactive threshold-based scaling logic is presented and evaluated.
Server clusters also need to reduce processing latency. Otherwise, subscribers experience low quality of service such as delayed call establishment, dropped calls, and inadequate media quality. Cloud computing platforms do not guarantee latency on virtual machines due to resource contention on the same physical host. These extra latencies from resource contention are temporary in nature. Therefore, we propose and evaluate a mechanism that temporarily distributes more incoming calls to responsive SIP proxies, based on measurements of the processing delay in proxies.
Availability of SIP server clusters is also a challenge on platforms where a node may fail anytime. We investigated how single component failures in a cluster can lead to a complete system outage. We found that for single component failures, simply having redundant components of the same type are enough to mask those failures. However, for client-facing components, smarter clients and DNS resolvers are necessary.
Throughout the thesis, a prototype SIP proxy cluster is re-used, with variations in the architecture or configuration, to demonstrate and address issues mentioned above. This allows us to tie all of our approaches for different issues into one coherent system that is dynamically scalable, is responsive despite latency varations of virtual machines, and is tolerant of single component failures in cloud platforms
Java, Java, Java: Object-Oriented Problem Solving
Open Access Textbook from Open Textbook Library:
Java, Java, Java, 3e was previously published by Pearson Education, Inc.
The first edition (2000) and the second edition (2003) were published by
Prentice-Hall. In 2010 Pearson Education, Inc. reassigned the copyright to
the authors, and we are happy now to be able to make the book available
under an open source license.
This PDF edition of the book is available under a Creative Commons
Attribution 4.0 International License, which allows the book to be used,
modified, and shared with attribution:
(https://creativecommons.org/licenses/by/4.0/).
– Ralph Morelli and Ralph Walde
– Hartford, CT
– December 30, 201