A language for semi-structured documents, XML has emerged as the core of the web services architecture, and is playing crucial roles in messaging systems, databases, and document processing. However, the processing of...
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ISBN:
(纸本)9781424403431
A language for semi-structured documents, XML has emerged as the core of the web services architecture, and is playing crucial roles in messaging systems, databases, and document processing. However, the processing of XML documents has a reputation for poor performance, and a number of optimizations have been developed to address this performance problem from different perspectives, none of which have been entirely satisfactory. In this paper, we present a seemingly quixotic, but novel approach: parallel XML parsing. Parallel XML parsing leverages the growing prevalence of multicore architectures in all sectors of the computer market, and yields significant performance improvements. this paper presents our design and implementation of parallel XML parsing. Our design consists of an initial preparsing phase to determine the structure of the XML document, followed by a full, parallel parse. the results of the preparsing phase are used to help partition the XML document for data parallel processing. Our parallel parsing phase is a modification of the libxml2 [1] XML parser, which shows that our approach applies to real-world, production quality parsers. Our empirical study shows our parallel XML parsing algorithm can improved the XML parsing performance significantly and scales well.
gridcomputing infrastructures are inherently dynamic and unpredictable environments shared by many users. grid schedulers aim to make efficient use of grid resources while providing the best possible performance to t...
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ISBN:
(纸本)9781424403431
gridcomputing infrastructures are inherently dynamic and unpredictable environments shared by many users. grid schedulers aim to make efficient use of grid resources while providing the best possible performance to the grid applications and satisfying the associated performance and policy constraints. Additionally, in commercial grid settings, where the grid resource brokering becomes an increasingly important part of grid scheduling, it is necessary to minimise the cost of application execution on the behalf of the grid users, while ensuring that the applications meet their QoS constraints. Efficient resource allocation could in turn also allow the resource broker to maximise it's profit by minimising the number of resources procured. Scheduling in such a large-scale, dynamic and distributed environment is a complex undertaking. In this paper, we propose an approach to grid scheduling which abstracts over the details of individual applications, focusing instead on the global cost optimisation problem and the scheduling of the entire grid workload. Our model places particular emphasis on the stochastic and unpredictable nature of the grid, leading to a more accurate reflection of the state of the grid and hence more efficient and accurate scheduling decisions.
Security underpins grids and e-Research. Without a robust, reliable and simple grid security infrastructure combined with commonly accepted security practices, large portions of the research community and wider indust...
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ISBN:
(纸本)9781424403431
Security underpins grids and e-Research. Without a robust, reliable and simple grid security infrastructure combined with commonly accepted security practices, large portions of the research community and wider industry will not engage. the predominant way in which security is currently addressed in the grid community is through Public Key Infrastructures (PKI) based upon X.509 certificates to support authentication. Whilst PKIs address user identity issues, authentication does not provide fine grained control over what users are allowed to do on remote resources (authorization). In this paper we outline how we have successfully combined Shibboleth and advanced authorization technologies to provide simplified (from the user perspective) but fine grained security for access to and usage of grid resources. We demonstrate this approach through different security focused e-Science projects being conducted at the National e-Science Centre (NeSC) at the University of Glasgow. We believe that this model will be more widely applicable and encourage the further uptake of e-Science by non-IT specialists in the research communities.
In this paper, we present a new extension and reinterpretation of one of the most successful models of awareness in Computer Supported Cooperative Work (CSCW), called the Spatial Model of Interaction (SMI), which mana...
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ISBN:
(纸本)9781424403431
In this paper, we present a new extension and reinterpretation of one of the most successful models of awareness in Computer Supported Cooperative Work (CSCW), called the Spatial Model of Interaction (SMI), which manage awareness of interaction through a set of key concepts, to manage task delivery in collaborative distributed systems. this model also applies some theoretical principles and theories of multi-agents systems to create a collaborative and cooperative environment that can be able to provide an autonomous, efficient and independent management of the amount of resources available in a grid environment. this model has been implemented using web services and some experimental results carried out over a real and heterogeneous grid are presented withthe end of emphasizing the performance speedup of the system using the AMBLE model.
the grid can be seen as a collection of services each of which performs some functionality. Users of the grid seek to use combinations of these services to perform the overall task they need to achieve. In general thi...
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ISBN:
(纸本)9781424403431
the grid can be seen as a collection of services each of which performs some functionality. Users of the grid seek to use combinations of these services to perform the overall task they need to achieve. In general this can be seen as a set of service with a workflow document describing how these services should be combined. the user may also have certain constraints on the workflow operations, such as execution time or cost to the user, specified in the form of a Quality of Service (QoS) document. the users submit their workflow to a brokering service along withthe QoS document. the brokering service's task is to map any given workflow to a subset of the grid services taking the QoS and state of the grid into account - service availability and performance. We propose in this paper an approach for generating constraint equations describing the workflow, the QoS requirements and the state of the grid. this set of equations may be solved using Mixed-Integer Linear Programming (MILP), which is the traditional method. We further develop a novel 2-stage stochastic MILP which is capable of dealing withthe volatile nature of the grid and adapting the selection of the services during the lifetime of the workflow. We present experimental results comparing our approaches, showing that the 2-stage stochastic programming approach performs consistently better than other traditional approaches.
In grid collaborations, scientists use middleware to execute computational experiments, visualize results, and securely share data on resources ranging from desktop machines to supercomputers. While there has been sig...
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ISBN:
(纸本)9781424403431
In grid collaborations, scientists use middleware to execute computational experiments, visualize results, and securely share data on resources ranging from desktop machines to supercomputers. While there has been significant effort in authentication and authorization for these distributed infrastructures, it is still difficult to determine, post-facto, exactly what information might have been accessed, what operations might have occurred, and for what reasons. To address this problem, we have designed and implemented a secure logging infrastructure for grid data access. We uniquely leverage and extend XacmL with new capabilities so that data owners can specify logging policies and these policies can be used to engage logging mechanisms to record events of interest to the data owners. A case study based on *** is presented and analyzed, utilizing both local storage of log records and remote storage via SAWS, an independently developed secure audit Web service. We show that with relatively little performance overhead, data owners are provided with new flexibility for determining the post-facto conditions under which their grid data was accessed.
In this article we examine the integration three emerging trends in Information Technology (Utility computing, gridcomputing, and Web Services) new computing paradigm (grid-based Application Service Provision) that i...
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ISBN:
(纸本)0769519946
In this article we examine the integration three emerging trends in Information Technology (Utility computing, gridcomputing, and Web Services) new computing paradigm (grid-based Application Service Provision) that is taking place in the context the European research project GRASP. In the first of the paper, we explain how the integration of emerging trends can support enterprises in creating competitive advantage. In the second part, we focus on grid-based Application Service Provision (GRASP), which builds a new technology-driven business paradigm on top of such integration. We conclude by outlining plan for prototyping a GRASP platform in the context an ongoing European research project.
this paper presents ongoing research and current results on the development of flexible access control infrastructures for complex resource provisioning in grid-based collaborative applications and on-demand network s...
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ISBN:
(纸本)9781424403431
this paper presents ongoing research and current results on the development of flexible access control infrastructures for complex resource provisioning in grid-based collaborative applications and on-demand network services provisioning. We investigate the use of workflow concepts for the required orchestration of multiple grid resources and/or services across multiple administrative and security domains. In particular, workflow execution and management tools can be used to track security context changes that are dependent on the application domain, execution stage defined policies, or user and/or service attributes. the paper discusses what specific functionality should be added to grid-oriented authorization frameworks to handle such dynamic service-related security contexts. As an example, the paper explains how such functionality can be achieved in the GAAA Authorization framework and GAAA toolkit. Suggestions are given about integration withthe Globus Toolkit's Authorization Framework. Additionally, the paper analyses what possibilities of expressing and handling dynamic security contexts are available in XacmL and SAML, and how the VO concept can be used for managing dynamic security associations of users and resources. the paper is based on experiences gained from major grid based and grid oriented projects such as EGEE, Nextgrid, *** and GigaPort Research on Network.
the transformations, analyses and interpretations of data in scientific workflows are vital for the repeatability and reliability of scientific workflows. this provenance of scientific workflows has been effectively c...
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ISBN:
(纸本)9781479978816
the transformations, analyses and interpretations of data in scientific workflows are vital for the repeatability and reliability of scientific workflows. this provenance of scientific workflows has been effectively carried out in grid based scientific workflow systems. However, recent adoption of Cloud-based scientific workflows present an opportunity to investigate the suitability of existing approaches or propose new approaches to collect provenance information from the Cloud and to utilize it for workflow repeatability in the Cloud infrastructure. the dynamic nature of the Cloud in comparison to the grid makes it difficult because resources are provisioned on-demand unlike the grid. this paper presents a novel approach that can assist in mitigating this challenge. this approach can collect Cloud infrastructure information along with workflow provenance and can establish a mapping between them. this mapping is later used to re-provision resources on the Cloud. the repeatability of the workflow execution is performed by: (a) capturing the Cloud infrastructure information (virtual machine configuration) along withthe workflow provenance, and (b) re-provisioning the similar resources on the Cloud and re-executing the workflow on them. the evaluation of an initial prototype suggests that the proposed approach is feasible and can be investigated further.
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