7,815 research outputs found
A Taxonomy of Workflow Management Systems for Grid Computing
With the advent of Grid and application technologies, scientists and
engineers are building more and more complex applications to manage and process
large data sets, and execute scientific experiments on distributed resources.
Such application scenarios require means for composing and executing complex
workflows. Therefore, many efforts have been made towards the development of
workflow management systems for Grid computing. In this paper, we propose a
taxonomy that characterizes and classifies various approaches for building and
executing workflows on Grids. We also survey several representative Grid
workflow systems developed by various projects world-wide to demonstrate the
comprehensiveness of the taxonomy. The taxonomy not only highlights the design
and engineering similarities and differences of state-of-the-art in Grid
workflow systems, but also identifies the areas that need further research.Comment: 29 pages, 15 figure
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Ratatoskr wide-area actuator RPC over gridstat with timeliness, redundancy, and safety
The development of the communication infrastructure for the north-American electrical powergrid has failed to fully incorporate important developments in the field of computer science,affecting the stability and efficiency of the power grid as a whole. The current power-gridcommunication standard, SCADA, utilizes protocols specialized for centralized communication,hampering communication between field sites key for envisioned improvements of power gridsafety and efficiency. Further, a number of different proprietary communication protocols are inuse, making communication between power utility companies very difficult.GridStat is a communication infrastructure designed for a power grid environment that solvesmany of the problems with the current situation. GridStat uses a specialization of thepublish-subscribe middleware paradigm, status dissemination, that takes advantage of thesemantics of status data to provide flexible acquisition of power-grid data with multipledimensions of QoS semantics. The middleware approach enables communication betweenutilities independent of proprietary network protocols, and allows enhanced network features such as forwarding data through multiple redundant paths. While GridStat provides excellent support for data acquisition, the publish-subscribe architecture supports only one-way communication and provides syntax and semantics unsuitable for control communications.This thesis presents Ratatoskr, a novel scheme for control of actuators using GridStat communication. It constructs a two-way communication channel on top of GridStatpublish/subscribe paths, and utilizes the QoS semantics and middleware properties GridStatprovides. For control communication Ratatoskr uses remote procedure call (RPC), providingprogrammer friendliness and familiarity. The QoS semantics of GridStat are drawn upon toprovide the timeliness required for power-grid operation. Reliability concerns are addressed byproviding three redundancy schemes, ACK/resend, transmitting multiple copies of a singlepacket, and spatial redundancy through GridStat’s redundant routing paths feature. Additionally,pre- and post-condition expressions over GridStat status variables are built into call semantics.The architecture and design of Ratatoskr is presented, along with results from an evaluation of aprototype implementation
Integration of Legacy Appliances into Home Energy Management Systems
The progressive installation of renewable energy sources requires the
coordination of energy consuming devices. At consumer level, this coordination
can be done by a home energy management system (HEMS). Interoperability issues
need to be solved among smart appliances as well as between smart and
non-smart, i.e., legacy devices. We expect current standardization efforts to
soon provide technologies to design smart appliances in order to cope with the
current interoperability issues. Nevertheless, common electrical devices affect
energy consumption significantly and therefore deserve consideration within
energy management applications. This paper discusses the integration of smart
and legacy devices into a generic system architecture and, subsequently,
elaborates the requirements and components which are necessary to realize such
an architecture including an application of load detection for the
identification of running loads and their integration into existing HEM
systems. We assess the feasibility of such an approach with a case study based
on a measurement campaign on real households. We show how the information of
detected appliances can be extracted in order to create device profiles
allowing for their integration and management within a HEMS
Flexible provisioning of Web service workflows
Web services promise to revolutionise the way computational resources and business processes are offered and invoked in open, distributed systems, such as the Internet. These services are described using machine-readable meta-data, which enables consumer applications to automatically discover and provision suitable services for their workflows at run-time. However, current approaches have typically assumed service descriptions are accurate and deterministic, and so have neglected to account for the fact that services in these open systems are inherently unreliable and uncertain. Specifically, network failures, software bugs and competition for services may regularly lead to execution delays or even service failures. To address this problem, the process of provisioning services needs to be performed in a more flexible manner than has so far been considered, in order to proactively deal with failures and to recover workflows that have partially failed. To this end, we devise and present a heuristic strategy that varies the provisioning of services according to their predicted performance. Using simulation, we then benchmark our algorithm and show that it leads to a 700% improvement in average utility, while successfully completing up to eight times as many workflows as approaches that do not consider service failures
Developing a distributed electronic health-record store for India
The DIGHT project is addressing the problem of building a scalable and highly available information store for the Electronic Health Records (EHRs) of the over one billion citizens of India
06121 Abstracts Collection -- Atomicity: A Unifying Concept in Computer Science
From 19.03.06 to 24.03.06, the Dagstuhl Seminar 06121 ``Atomicity: A Unifying Concept in Computer Science\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general.
Links to extended abstracts or full papers are provided, if available
A Classification of BPEL Extensions
The Business Process Execution Language (BPEL) has emerged as de-facto standard for business processes implementation. This language is designed to be extensible for including additional valuable features in a standardized manner. There are a number of BPEL extensions available. They are, however, neither classified nor evaluated with respect to their compliance to the BPEL standard. This article fills this gap by providing a framework for classifying BPEL extensions, a classification of existing extensions, and a guideline for designing BPEL extensions
Advancing Operating Systems via Aspect-Oriented Programming
Operating system kernels are among the most complex pieces of software in existence to-
day. Maintaining the kernel code and developing new functionality is increasingly compli-
cated, since the amount of required features has risen significantly, leading to side ef fects
that can be introduced inadvertedly by changing a piece of code that belongs to a completely
dif ferent context.
Software developers try to modularize their code base into separate functional units.
Some of the functionality or “concerns” required in a kernel, however, does not fit into
the given modularization structure; this code may then be spread over the code base and
its implementation tangled with code implementing dif ferent concerns. These so-called
“crosscutting concerns” are especially dif ficult to handle since a change in a crosscutting
concern implies that all relevant locations spread throughout the code base have to be
modified.
Aspect-Oriented Software Development (AOSD) is an approach to handle crosscutting
concerns by factoring them out into separate modules. The “advice” code contained in
these modules is woven into the original code base according to a pointcut description, a
set of interaction points (joinpoints) with the code base.
To be used in operating systems, AOSD requires tool support for the prevalent procedu-
ral programming style as well as support for weaving aspects. Many interactions in kernel
code are dynamic, so in order to implement non-static behavior and improve performance,
a dynamic weaver that deploys and undeploys aspects at system runtime is required.
This thesis presents an extension of the “C” programming language to support AOSD.
Based on this, two dynamic weaving toolkits – TOSKANA and TOSKANA-VM – are presented
to permit dynamic aspect weaving in the monolithic NetBSD kernel as well as in a virtual-
machine and microkernel-based Linux kernel running on top of L4. Based on TOSKANA,
applications for this dynamic aspect technology are discussed and evaluated.
The thesis closes with a view on an aspect-oriented kernel structure that maintains
coherency and handles crosscutting concerns using dynamic aspects while enhancing de-
velopment methods through the use of domain-specific programming languages
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