1,721,183 research outputs found
Systems support for distributed learning environments
Get PDFThis thesis contends that the growing phenomena of multi-user networked "learning environments" should be treated as distributed interactive systems and that their developers should be aware of the systems and networks issues involved in their construction and maintenance. Such environments are henceforth referred to as distributed learning environments, or DLEs. Three major themes are identified as part of systems support: i) shared resource coherence in DLEs; ii) Quality of Service for the end- users of DLEs; and iii) the need for an integrating framework to develop, deploy and manage DLEs. The thesis reports on several distinct implementations and investigations that are each linked by one or more of those themes. Initially, responsiveness and coherence emerged as potentially conflicting requirements, and although a system was built that successfully resolved this conflict it proved difficult to move from the "clean room" conditions of a research project into a real world learning context. Accordingly, subsequent systems adopted a web-based approach to aid deployment in realistic settings. Indeed, production versions of these systems have been used extensively in credit-bearing modules in several Scottish Universities. Interactive responsiveness then emerged as a major Quality of Service issue in its own right, and motivated a series of investigations into the sources of delay, as experienced by end users of web-oriented distributed learning environments. Investigations into this issue provided insight into the nature of web-oriented interactive distributed learning and highlighted the need to be QoS-aware. As the volume and the range of usage of distributed learning applications increased the need for an integrating framework emerged. This required identifying and supporting a wide variety of educational resource types and also the key roles occupied by users of the system, such as tutors, students, supervisors, service providers, administrators, examiners. The thesis reports on the approaches taken and lessons learned from researching, designing and implementing systems which support distributed learning. As such, it constitutes a documented body of work that can inform the future design and deployment of distributed learning environments
A scalable architecture for the demand-driven deployment of location-neutral software services
Get PDFThis thesis presents a scalable service-oriented architecture for the demand-driven deployment of location-neutral software services, using an end-to-end or ‘holistic’ approach to address identified shortcomings of the traditional Web Services model. The architecture presents a multi-endpoint Web Service environment which abstracts over Web Service location and technology and enables the dynamic provision of highly-available Web Services. The model describes mechanisms which provide a framework within which Web Services can be reliably addressed, bound to, and utilized, at any time and from any location. The presented model eases the task of providing a Web Service by consuming deployment and management tasks. It eases the development of consumer agent applications by letting developers program against what a service does, not where it is or whether it is currently deployed. It extends the platform-independent ethos of Web Services by providing deployment mechanisms which can be used independent of implementation and deployment technologies. Crucially, it maintains the Web Service goal of universal interoperability, preserving each actor’s view upon the system so that existing Service Consumers and Service Providers can participate without any modifications to provider agent or consumer agent application code. Lastly, the model aims to enable the efficient consumption of hosting resources by providing mechanisms to dynamically apply and reclaim resources based upon measured consumer demand
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
Program construction and evolution in a persistent integrated programming environment.
Get PDFIn orthogonally persistent systems, data is treated independently of its persistence allowing storage management details to be ignored by programmers. The coexistence of all data within a persistent repository provides new opportunities for the persistent environment to participate in a number of software engineering processes, namely, software:
. construction,
. debugging,
. maintenance,
. evolution, and
. distribution.
A novel programming methodology supporting various styles of binding allows the persistent environment to participate in the software construction process. Existing programs and data may be bound to an application at different times during the application's lifetime, namely, at run-time, compile-time and program construction-time. This wide range of binding styles enables. the programmer to trade off binding safety and binding flexibility. A mechanism called Octopus enables the programmer to access a rich source of information about the bindings within arbitrary values. Using this information, existing applications may be interrogated and manipulated in ways in which the programming language alone would not normally permit. However, Octopus ensures that the type system of the programming language remains inviolate, thus providing a type safe mechanism for constructing debugging, maintenance and evolutionary tools. Another feature of Octopus is that it permits portions of an application's object graph to be isolated and transmitted. Nodules permit a style of template programming that enables data values and executable code to be shared between different Nodule instances. The essence of this mechanism is to allow programs to be constructed and compiled without the requirement that the values used by the program be present. In this manner, individual components may be constructed independently and later assembled to form a complete application. Nodules also provide a rich source of information about the structure of an application and may be used in conjunction with Octopus to develop and maintain software components. This thesis describes in detail a persistent programming environment, the Octopus and Nodule mechanisms, and illustrates how each of these mechanisms, when used in conjunction with each other, provide a persistent integrated programming environment that supports a wide variety of software engineering activities otherwise lacking in conventional, or non-persistent systems.Thesis (Ph.D.) -- University of Adelaide, Faculty of Engineering, 199
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
A methodology for developing and deploying distributed applications
No full textWe describe a methodology for developing and deploying distributed Java applications using a reflective middleware system called RAFDA. We illustrate the methodology by describing how it has been used to develop a peer-to-peer infrastructure, and explain the benefits relative to other techniques. The strengths of the approach are that the application logic can be designed and implemented completely independently of distribution concerns, easing the development task, and that this gives great flexibility to alter distribution decisions late in the development cycle
A flexible, policy-aware middleware system
No full textMiddleware augments operating systems and network infrastructure to assist in
the creation of distributed applications in a heterogeneous environment. Current
middleware systems exhibit some or all of the following five main problems:
1. Decisions must be made early in the design process.
2. Applications are inflexible to dynamic changes in their distribution.
3. Application development is complex and error-prone.
4. Existing systems force an unnatural encoding of application-level semantics.
5. Approaches to the specification of distribution policy are limited.
This thesis defines a taxonomy of existing middleware systems and describes their
limitations. The requirements that must be met by a third generation middleware system
are defined and implemented by a system called the RAFDA Run-Time (RRT). The RRT
allows control over the extent to which inter-address-space communication is exposed to
programmers, aiding the creation, maintenance and evolution of distributed applications.
The RRT permits the introduction of distribution into applications quickly and
with minimal programmer effort, allowing for quick application prototyping.
Programmers can conceal or expose the distributed nature of applications as required. The RRT allows instances of arbitrary application classes to be exposed to remote access as Web Services, provides control over the parameter-passing semantics applied to
remote method calls and permits the creation of flexible distribution policies. The design of the RRT is described and evaluated qualitatively in the context of a case study based around the implementation of a peer-to-peer overlay network. A prototype implementation of the RRT is examined and evaluated quantitatively.
Programmers determine the trade off between flexibility and simplicity offered by
the RRT on a per-application basis, by concealing or exposing inter-address-space
communication. The RRT is a middleware system that adapts to the needs of applications, rather than forcing distributed applications to adapt to the needs of the middleware system
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