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Now showing items 1-20 of 76

A graphical deployment and management tool for distributed applications

Andersen, Anders; Aanensen, Thomas (Research report; Forskningsrapport, 2005)

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Abstract:

OOPP is a component based middleware platform with support for complex distributed applications. The main goal of OOPP is to create an expressive programming model for distributed applications where by default details are hidden for the programmer. When necessary, reflection is used to expose and sometimes modify these details. All interaction with an OOPP component are specified by its component model and a at set of well-defined interfaces. The component model specifies how a component interacts with the runtime. The set of interfaces specifies how a component interacts with other components. An OOPP application is created by combining a set of OOPP components. OOPP Studio can be used to create and manage such an application. This paper gives an overview of the OOPP programming model and discusses in more details OOPP Studio. OOPP Studio is a powerful graphical tool used to build, deploy, and manage a distributed OOPP application.

URI:

http://hdl.handle.net/10037/390

File(s) in this item: 1

report.pdf (210.2Kb)

Authorization and access control in a distributed file repository

Arild, Ronny; Stabell-Kulø, Tage (Research report; Forskningsrapport, 18-Jan-1999)

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Abstract:

A distributed file repository is described. It supports interaction between different machines used by a single user, as well as between users that share data. Files can be replicated and consistency will be maintained, or files can be shipped (copied) to a remote site. As with more traditional systems, the servers are trusted not to leak information. However, the rôle servers play is not as much the hub in the system. In particular, users are in charge of delegating acccess to files. For flexibility, delegations might take place outside of the realm of the system proper; by any means available to the users. Users can delegate access rights to local and remote users, including remote users in other domains. ACLs are used to maintain local access control; capabilities are used to access remote files. These capabilities are valid within epochs, but are immediately revoked when being used, thus being valid at-most-once. In essence, we have realized a flexible infrastructure where users can implement their own security policy.

URI:

http://hdl.handle.net/10037/360

File(s) in this item: 1

report.pdf (261.1Kb)

The xTrans Transaction Model and FlexCP Commit Protocol

Arntsen, Anna-Brith (Research report; Forskningsrapport, 2006)

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Abstract:

Traditionally, transactions are flat and atomic possessing the ACID properties. The traditional ACID transaction model has clear limitations in new application domains where transactions often are long-running and require properties that go beyond ACID. Structuring a long-running transaction as an ACID transaction will impede both performance and concurrency. To meet extended and varying transactional requirements, we have described a flexible transaction model, the xTrans model, providing support for both ACID and non-ACID properties. Further, current transaction processing systems in distributed environments are inflexible with respect to supporting extended transactions. Thus, to assist in the execution of, among others, xTrans transactions, we have designed a flexible commit protocol: FlexCP. This report presents the xTrans transaction model and the FlexCP commit protocol.

URI:

http://hdl.handle.net/10037/393

File(s) in this item: 1

report.pdf (342.0Kb)

A programmable structure for pervasive computing

Arntzen, Ingar Mæhlum; Johansen, Dag (Research report; Forskningsrapport, 2004)

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Abstract:

This exstended abstract presents an asymmetric and programmable (extensible) approach to pervasive computing. The idea is to off-load computations from light portable clients into a back-bone of seamlessly integrated servers. This way, a user can extend and personalize his pervasive computational environment by installing computations following his trajectory throughout the day. Focus on this extended abstract is on structural issues related to the back-end servers running mobile code off-loaded from the mobile user.

URI:

http://hdl.handle.net/10037/374

File(s) in this item: 1

report.pdf (57.07Kb)

Performance experiments with the Storm View Distributed Parallel Volume Renderer.

Asplin, Jo; Johansen, Dag (Research report; Forskningsrapport, Jun-1995)

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Abstract:

Volume rendering is a useful but cpu-intensive method for visualizing large scalar fields. The time to render a single image may be reduced by parallel processing. This paper reports on performance experiments with the StormView volume renderer, which is parallelized on a set of 57 MIPS / 17 MFLOPS workstations connected by a 10 Mbps Ethernet. For certain user patterns, we show that our parallelization exhibits substantial speedups. We compare the performance of a dynamic and a static load balancing algorithm.

URI:

http://hdl.handle.net/10037/384

File(s) in this item: 1

report.pdf (383.3Kb)

On the design and performance of the PARFUM Parallel Fault Tolerant Volume Renderer

Asplin, Jo; Mehus, Sindre (Research report; Forskningsrapport, Jan-1997)

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Abstract:

Volume rendering is an important and CPU-intensive technique for visualizing large scalar fields. In essence, a volume renderer performs two activites on behalf of the user: loading a new data set, and rendering the current one. At one level, the performance of an individual activity is important. At another level, the erformance of the session as a whole, in particular switching from one activity to the next, should be addressed. In this paper we present PARFUM, a parallel volume renderer based on a controller/worker model in a network of workstations. PARFUM has three essential properties that increase the performance of a parallel volume renderer. First, dynamic load balancing is employed during a rendering activity. Second, workers may enter or fail without affecting the correctness of a session. Third, a user may easily abort the current activity in favour of a new one. These properties may more easily be achieved by accepting (rather than fighting) the inherent asynchrony in a distributed system. As a consequence, PARFUM attempts to minimize causal dependencies in the interaction between the user and the controller as well as between the controller and the workers. We evaluate two implementations based on the TCP and UDP transport protocols respectively.

URI:

http://hdl.handle.net/10037/375

File(s) in this item: 1

report.pdf (336.4Kb)

Using a virtual event space to understand parallel application communication behavior

Bongo, Lars Ailo; Anshus, Otto J.; Bjørndalen, John Markus (Research report; Forskningsrapport, 2003)

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Abstract:

We have developed EventSpace, a configurable data collecting, management and observation system for monitoring low-level synchronization and communication events with the purpose of understanding the behavior of parallel applications on clusters and multi-clusters. Applications are instrumented by adding data collecting code in the form of event collectors to an applications communication paths. When triggered these create and store virtual events to a virtual event space. Based on the meta-data describing the communication paths, virtual events can be combined to provide different views of the applications communication behavior. We used the data collected by EventSpace to do a post-mortem analysis of a wind-tunnel application, a river simulator, global clock synchronization, and a hierarchical barrier benchmark. The views allowed us to detect anomalous communication behavior, detect load balance problems, analyze hierarchical barriers, synchronize the Pentium timestamp counters on the cluster nodes, and analyze the accuracy of the synchronization.

URI:

http://hdl.handle.net/10037/366

File(s) in this item: 1

report.pdf (286.6Kb)

Evaluating the performance of the allreduce collective operation on clusters. Approach and results

Bongo, Lars Ailo; Anshus, Otto J.; Bjørndalen, John Markus (Research report; Forskningsrapport, 2004)

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Abstract:

The performance of the collective operations provided by a communication library is important for many applications run on clusters. The communication structure of collective operations can be organized as a tree. Performance can be improved by configuring and mapping the tree to the clusters in use. We describe and demonstrate an approach for evaluating the performance of different configurations and mappings of allreduce run on clusters of different size, consisting of single-CPU hosts, and SMPs with a different number of CPUs. A breakdown of the cost of allreduce using the best configuration on different clusters is provided. For all, the broadcast part is more expensive than the reduce part. Inter-host communication contributes more to the time per allreduce than the synchronization in the allreduce components. For the small messages sizes used (4 and 256 bytes), the time spent computing the partial reductions is insignificant. Reconfiguring hierarchy aware trees improved performance up to a factor of 1.49, by avoiding scalability problems of the components on SMPs, and by finding the right balance between available concurrency, load on 'root' hosts and the number of network links in a tree. Extending a tree by adding more threads, or by combining two trees does not have a negative influence on the performance of a configuration, but increasing message size does.

URI:

http://hdl.handle.net/10037/372

File(s) in this item: 1

report.pdf (152.3Kb)

The Longcut Wide Area Network Emulator. Design and Evaluation

Bongo, Lars Ailo (Research report; Forskningsrapport, 2005)

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Abstract:

Experiments run on a Grid, consisting of clusters administered by multiple organizations connected by shared wide area networks (WANs), may not be reproducible. First, traffic on the WAN cannot be controlled. Second, allocating the same resources for subsequent experiments can be difficult. Longcut solves both problems by splitting a single cluster into several parts, and for each part having one node emulating a WAN link by delaying messages sent through it. The delay is calculated using latency and bandwidth measurements collected using the Network Weather Service and a parallel application monitor. We evaluate the precision, usability for WAN collective operation research, and scalability of Longcut.

URI:

http://hdl.handle.net/10037/381

File(s) in this item: 1

report.pdf (131.5Kb)

Modeling Prognostic Factors in Resectable Pancreatic Adenocarcinomas

Botsis, Taxiarchis; Anagnostou, Valsamo K.; Hripcsak, George; Hartvigsen, Gunnar; Weng, Chunhua (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)

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URI: http://hdl.handle.net/10037/3344

File(s) in this item: 1

article.pdf (1.051Mb)
Sixteen years of ICPC use in Norwegian primary care : looking through the facts

Bassøe, Carl-Fredrik; Botsis, Taxiarchis; Hartvigsen, Gunnar (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)

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URI: http://hdl.handle.net/10037/3097

File(s) in this item: 1

article.pdf (847.7Kb)

Engineering push-based web services

Brenna, Lars; Johansen, Dag (Research report; Forskningsrapport, 2005)

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Abstract:

Much of the content of popular Internet information sources is highly dynamic: urgent in nature and sometimes relevant only for a short time. The typical approach to querying such dynamic sources is polling for updates often.1 This strains the traditional pull-based Internet and wastes network resources on transmitting redundant information. This paper focuses on how to structure the Internet to avoid the unnecessary client-server interactions dominating the Internet. To that end, we extend the API of popular existing Internet services trough Web service wrappers. These wrappers use the API of, for instance, Google, but provide functionality that is richer. Initial experience shows that major performance gains can be achieved through this approach.

URI:

http://hdl.handle.net/10037/385

File(s) in this item: 1

report.pdf (293.4Kb)

Features of Mobile Diabetes Applications: Review of the Literature and Analysis of Current Applications Compared Against Evidence-Based Guidelines

Chomutare, Taridzo; Fernandez-Luque, Luis; Årsand, Eirik; Hartvigsen, Gunnar (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)

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Abstract:

Background: Interest in mobile health (mHealth) applications for self-management of diabetes is growing. In July 2009, we found 60 diabetes applications on iTunes for iPhone; by February 2011 the number had increased by more than 400% to 260. Other mobile platforms reflect a similar trend. Despite the growth, research on both the design and the use of diabetes mHealth applications is scarce. Furthermore, the potential influence of social media on diabetes mHealth applications is largely unexplored. Objective: Our objective was to study the salient features of mobile applications for diabetes care, in contrast to clinical guideline recommendations for diabetes self-management. These clinical guidelines are published by health authorities or associations such as the National Institute for Health and Clinical Excellence in the United Kingdom and the American Diabetes Association.

URI:

http://hdl.handle.net/10037/3942

File(s) in this item: 1

article.pdf (337.1Kb)

Measuring Physical Activity with Sensors : A Qualitative Study

Fisterer, Bernhard; Dias, Andrê Fernando; Lamla, Gregor; Hartvigsen, Gunnar; Horsch, Alexander; Kuhn, Klaus A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)

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URI: http://hdl.handle.net/10037/3129

File(s) in this item: 1

article.pdf (236.4Kb)

Pesto flavoured security

Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, May-2002)

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Abstract:

Pesto aims at providing highly available and secure storage for longlived data to mobile users roaming into untrusted environments. Security in Pesto encompasses the following three aspects: availability, safety, and privacy. A mechanism supporting one aspect may adversely affect another. For example, replication may increase availability but complicates supporting confidentiality, and simply encrypting data for confidentiality may defeat the whole purpose of replication. We show that an integral approach to these aspects leads to considerable savings in overall system complexity, and thus to a more secure system. In Pesto, users may specify different levels of trust in different parts of the infrastructure. In particular, a user may trust a node to merely store (encrypted) data, and/or to distribute replicas to other nodes on his behalf, and/or he may trust a node to enforce access control on his behalf to his (plaintext) content. This report gives an overview of the main security mechanisms that makes this separation of concerns possible. We present its novel encryption framework and its trust management and discuss how it can be used to build distributed infrastructures with advanced security and safety properties.

URI:

http://hdl.handle.net/10037/364

File(s) in this item: 1

report.pdf (135.8Kb)

The taste of Pesto

Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, Aug-2001)

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Abstract:

The Pesto distributed storage platform is geared towards a computing model where private machines play a pivotal r ˆ ole. We argue that no centralized solutions are acceptable in its design and that it supports allocation of separate tasks to separate system components found in its target environment. Hence, Pesto separates trust from responsibility, storage from access control policy, and replication from consistency control. Pesto is designed around a few clean-cut abstractions, that make the above separations possible and efficient to implement. This report gives an overview of the main tasks typically supported by a distributed storage system, how Pesto supports these, how Pesto separates these from each other and what benefits such separation of concerns provides.

URI:

http://hdl.handle.net/10037/362

File(s) in this item: 1

report.pdf (147.3Kb)

The Pesto project. Goals and motivation

Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, Jun-2001)

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Abstract:

Pesto is a storage system geared towards a computing model where private machines play a pivotal role. Sharing of data is crucial, both between partners, and between the many devices owned by individual users. Replication is the only sensible means to provide ubiquitous access to private data. However, without provisions, replication endangers privacy by enlarging the Trusted Computing Base. The Pesto project aims at investigating security and safety issues in concert, such that security and safety measures and mechanisms can be identified that strengthen each other and, when that is not possible, to identify tradeoffs between safety and security of data in distributed systems. This report introduces the Pesto project and system; the motivation behind it and its design goals.

URI:

http://hdl.handle.net/10037/361

File(s) in this item: 1

report.pdf (107.5Kb)

QoS applied to security in mobile computing

Fallmyr, Terje; Stabell-Kulø, Tage (Research report; Forskningsrapport, 30-Jun-1997)

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Abstract:

Hand-held mobile computers have the potential to become important communication tools for roaming users. As such, they will also become very personal. They will be used under a wide range of operating conditions, and tight user control will be enforced on issues like power consumption, consistency control, and trust management. Their ability to adapt will be the key to their success. In this paper we outline our notion and use of Quality of Service (QoS) to the design of adaptive software systems for mobile computers. They have been developed in the MobyDick and GDD projects. We do not emphasize on the provision of QoS guarantees. In stead, our notion of QoS is used to convey relevant and timely management information between service users and providers on the correct abstraction level. It structures adaptability management in the hand held machine, and it captures adaptability to changes both stemming from the hosting environment and user commands. As an example of how the architecture works, the importance of adaptivity of security services for personal companions are explained, and we show how our notion of QoS may realize adaptable security services.

URI:

http://hdl.handle.net/10037/373

File(s) in this item: 1

report.pdf (102.9Kb)

Increased scalability of the StormCast distributed application

Farsi, V. (Research report; Forskningsrapport, Sep-1994)

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Abstract:

Scaling is recognized as a primary concern in developing distributed applications. Scaling problems occur when an application reach its upper boundary in some way or another. This paper describes the considerations made in the redesign of the StormCast distributed application to achieve more scalability. Naturally, there can be many factors that restrict a system's scalability. The challenge meeting the designers of distributed applications is to limit the influence of such factors. In this paper we focus on modularity, decentralized approach to design of application, transparent naming, caching of information, replicated data and services in order to enhance scalability.

URI:

http://hdl.handle.net/10037/397

File(s) in this item: 1

report.pdf (164.6Kb)

Satellite communication applied in a distributed application

Farstad, Werner; Johansen, Dag; Hartvigsen, Gunnar (Research report; Forskningsrapport, Dec-1994)

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Abstract:

The paper describes the development of a prototype application for access to vital weather information from the Northern Atlantic sea region. The application gives meteorologists access to weather observations measured on sea vessels. Today the available information is very limited. On a daily basis, only 4-5 weather observations in the whole arctic sea-region are conducted. It is therefore suggested to use the available fishing-boat and the coast-guard as a basis for a full scale application. Communication is based on the Inmarsat-C global satellite system. This kind of communication offers limited data bandwidth, currently 600 bit/sec. In addition delays are introduced by the coast/earth-station due to message-queues and protocol-transformations. Based on the services of fered by the Inmarsat-C system, a simple prototype communication mechanism for data communication between terrestrial computers and computers on sea-vessels has been developed. It is, partly due to the nature of the satellite system, based on unreliable multicast of messages. A message may consist of a request which requires a reply (multicast RPC). Test results showed that doing a request and getting a reply takes from 1.5 - 4 minutes. The results depend on the type of message (supported by the Inmarsat-C system) which is used. The sea-vessels send weather observations in set intervals. This means higher availability on weather observations, and again a big step for meteorologists which today have to rely on observation which may be several hours old (if any at all).

URI:

http://hdl.handle.net/10037/394

File(s) in this item: 1

report.pdf (258.0Kb)

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Browsing Artikler, rapporter og annet (informatikk) by Author

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