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Browsing Artikler, rapporter og annet (informatikk) by Author
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Now showing items 72-76 of 76
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Blair, Gordon S.; Yang, Jie; Andersen, Anders (Research report; Forskningsrapport, 2005)[+][-]
Abstract: It is becoming clear that modern middleware platforms must provide both deploy-time configuration and run-time reconfiguration to accommodate rapid changing requirements and also to be able to operate in dynamic environments. J2EE is a key example of a middleware architecture that supports enterprise applications via its Enterprise JavaBeans (EJB) component model. EJB provides limited configurability in terms of a fixed set of non-functional middleware services at deployment-time (via a declarative deployment descriptor). However, EJB along with other related enterprise architectures generally do not provide enough support for re-configuration or evolution. At best, there is limited support in some platforms for replacing or updating particular services. This paper discusses the design of configurable and re-configurable middleware architecture and also the key role of separation of concerns for such platforms. The paper also describes the Arctic Beans component model which uses the Composition Filters model to capture such concerns and also support their safe composition.The paper also explains how this model can be used to construct an Arctic Beans container, in the style of EJB. The main contribution of the paper is to demonstrate that adaptable middleware platform can be developed using separation of concern technologies, specifically the composition filters model. URI: http://hdl.handle.net/10037/396 File(s) in this item: 1
report.pdf (335.0Kb) -
Yom-Tov, Elad; Fernandez Luque, Luis; Weber, Ingmar; Crain, Steven P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: There is widespread use of the Internet to promote anorexia as a lifestyle choice. Pro-anorexia content can be harmful for people affected or at risk of having anorexia. That movement is actively engaged in sharing photos on social networks such as Flickr. Objective: To study the characteristics of the online communities engaged in disseminating content that encourages eating disorders (known as “pro-anorexia”) and to investigate if the posting of such content is discouraged by the posting of recovery-oriented content. The extraction of pro-anorexia and pro-recovery photographs from the photo sharing site Flickr pertaining to 242,710 photos from 491 users and analyzing four separate social networks therein. Pro-anorexia and pro-recovery communities interact to a much higher degree among themselves than what is expected from the distribution of contacts (only 59-72% of contacts but 74-83% of comments are made to members inside the community). Pro-recovery users employ similar words to those used by pro-anorexia users to describe their photographs, possibly in order to ensure that their content appears when pro-anorexia users search for images. Pro-anorexia users who are exposed to comments from the opposite camp are less likely to cease posting pro-anorexia photographs than those who do not receive such comments (46% versus 61%), and if they cease, they do so approximately three months later. Our observations show two highly active communities, where most interaction is within each community. However, the pro-recovery community takes steps to ensure that their content is visible to the pro-anorexia community, both by using textual descriptions of their photographs that are similar to those used by the pro-anorexia group and by commenting to pro-anorexia content. The latter activity is, however, counterproductive, as it entrenches pro-anorexia users in their stance. Our results highlight the nature of pro-anorexia and pro-recovery photo sharing and accentuate the need for clinicians to be aware of such content and its effect on their patients. Our findings suggest that some currently used interventions are not useful in helping pro-anorexia users recover. Thus, future work should focus on new intervention methods, possibly tailored to individual characteristics. URI: http://hdl.handle.net/10037/5053 File(s) in this item: 1
article.pdf (369.0Kb) -
Zagorodnov, Dmitrii; Johansen, Dag (Research report; Forskningsrapport, 2004)[+][-]
Abstract: Events injected by publishers into a publish/subscribe system may reach users through a variety of devices: a stationary desktop, a laptop, a mobile phone, etc. We argue that the "last hop" -- from the network to the output device -- has unique properties, owing to the mobile nature of these devices, and as such demands special consideration. In particular, user's preferences and location may limit what should be forwarded to a device. Furthermore, technological constraints, such as network bandwidth availability and battery power, suggest that the decision when to forward messages is also important for optimizing user's experience. We describe a new publish/subscribe system with volume-limiting mechanisms and explain how user preferences, context, and device constraints can be accommodated in such a system. Notably, based on results of simulations, we propose a simple algorithm for low-cost "prefetching" of notifications to mobile devices in cases when network bandwidth is insufficient. URI: http://hdl.handle.net/10037/380 File(s) in this item: 1
report.pdf (183.5Kb) -
Zagorodnov, Dmitrii (Research report; Forskningsrapport, 2005)[+][-]
Abstract: The main purpose of this paper is to illuminate two types of unwanted traffic in a publish/subscribe system -- malicious (spam, DoS attacks) and vain (unused events) -- and suggest a general mechanism for minimizing their effects. We do this by augmenting the classic publish/subscribe interface with volume-limiting parameters -- a combination of attributes assigned to events by publishers and thresholds specified by subscribers -- and consider the implications of this interface on the unwanted traffic and on the routing infrastructure. Notably, we observe that this mechanism can minimize unwanted traffic without total access control if the routing substrate supports two properties: flow control and routing integrity. URI: http://hdl.handle.net/10037/386 File(s) in this item: 1
report.pdf (35.97Kb) -
Marzullo, Keith; Zagorodnov, Dmitrii; Alvisi, Lorenzo; Bressoud, Thomas C. (Research report; Forskningsrapport, 25-Aug-2005)[+][-]
Abstract: This article describes an architecture that allows a replicated service to survive crashes without breaking its TCP connections. Our approach does not require modifications to the TCP protocol, to the operating system on the server, or to any of the software running on the clients. Furthermore, it runs on commodity hardware. We compare two implementations of this architecture – one based on primary/backup replication and another based on message logging – focusing on scalability, failover time, and application transparency. We evaluate three types of services: a file server, a web server, and a multimedia streaming server. Our experiments suggest that the approach incurs low overhead on throughput, scales well as the number of clients increases, and allows recovery of the service in near-optimal time. URI: http://hdl.handle.net/10037/388 File(s) in this item: 1
report.pdf (296.0Kb)
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