Computational Grids have been identified as one of the paradigms revolutionizing the discipline of distributed computing. The contributions within the Grid community have resulted in new Grid technologies and continuous improvements to Grid standards and protocols. Though crucial to the success of the Grid approach, such an incremental evolution of Grid standards has become a primary cause of frustration for scientific and commercial application communities aspiring to adopt the Grid paradigm. Motivated by our rich experience and the need to decouple the application development and the Grid technology development processes, we propose an abstraction-based Grid middleware layer as part of the Java CoG Kit. In this paper, we showcase our abstraction model and verify its extensibility by integrating it with an advanced quality-of-service-based execution framework.

This chapter contains sections titled: Motivation for Evaluating Trust Service Trust – What is it? The Communication Model Trust Definition Service Provider Trust Service Consumer Trust Limitations of Current Approaches Evidence Ware Trust Model The System Life Cycle The Reputation Interrogation Phase (RIP) The SLA Negotiation Phase The Trust Verification Phase (TVP) Conclusion Reference The service-oriented architecture generally, and web services in particular, have become important research areas in distributed and grid computing. The use of these approaches often requires a developer to re-evaluate interactions between software components within their application. The service-oriented approach necessitates delegating control (and reliance on the results generated) to a third party – and this is often a limiting factor in the adoption of such approaches. Hence this lack of presence and visibility within organizational transactions, resulting from the use of services, may lead to a feeling of distrust and vulnerability. At the same time the increase in physical distance is a key opportunity for the deployment of new services. For these reasons a significant number of users have started to realize the importance of “trust” management for supporting business and scientific interactions electronically in service-oriented architectures. This chapter investigates the role of “trust” and “reputation” in the context of service provision and use, and proposes an architecture for utilizing these concepts in scientific applications.

Grid computing provides a robust paradigm for aggregating disparate resources in a secure and controlled environment. The emerging grid infrastructure gives rise to a class of scientific applications and services in support of collaborative and distributed resource-sharing requirements, as part of teleimmersion, visualization and simulation services. Because such applications operate in a collaborative mode, data must be stored, processed and delivered in a timely manner. Such classes of applications have collaborative and distributed resource-sharing requirements, and have stringent real-time constraints and quality-of-service (QoS) requirements. A QoS management approach is therefore essential to orchestrate and guarantee the interaction among such applications in a distributed computing environment. Grid architectures require an underpinning of QoS support to manage complex computation-intensive and data-intensive applications, as current grid middleware solutions lack QoS provision. QoS guarantees in the grid context have, however, not been given the importance they merit. To enhance its functionality, a computational grid must be overlaid with an advanced QoS architecture to best execute those applications with real-time constraints. This thesis reports on the design and implementation of a software framework, called Grid QoS Management (G-QoSm). G-QoSm incorporates a new QoS management model and provides a service-oriented QoS management approach that supports the Open Grid Service Architecture. Its novel features include grid-service discovery based on QoS attributes, immediate and advance resource reservation, service execution with QoS constraints, and techniques for QoS adaptation to compensate for resource degradation, and to optimise resource allocation while maintaining a service level agreement. The benefits of G-QoSm are demonstrated by prototype test-beds that integrate scientific grid applications and simulate grid data-transfer applications. Results show that the grid application and the data-transfer simulation have better performance when used with the proposed QoS approach. QoS abstractions are presented for building QoS-aware applications, in the context of service-oriented grids. These abstractions are application programming interfaces to facilitate application developers utilising the proposed QoS management solution.

Grid computing provides a global-scale distributed computing infrastructure for executing scientific and business applications. An important requirement is the need to make this infrastructure appear as a single logical coordinated resource – which in reality consists of a variety of resources aggregated across different administrative domains. The aggregation of network resources is often undertaken over a ‘best effort’ infrastructure as provided by the Internet – however many applications, which necessitate soft-real time constraints, such as collaborative working or remote visualisation, require more stringent traffic guarantees. Managing Quality of Service (QoS) requirements across these aggregated resources therefore becomes an important concern. Such QoS criteria must extend to computational, data and network resources, and are often expressed in a Service Level Agreement, multiples of which may co-exist over the entire collection of resources. In this paper we focus on network QoS as part of our wider work on the Grid QoS Management (G-QoSm) framework. Provisioning of such QoS support is provided via the Differentiated Services architecture, and relies on the use of a Bandwidth Broker (BB) component. Performance results of using the BB alongside other elements in G-QoSm are presented.

Grid computing provides the infrastructure necessary to access and use distributed resources as part of virtual organizations. When used in this way, Grid computing makes it possible for users to participate in collaborative and distributed applications such as tele-immersion, visualization, and computational simulation. Some of these applications operate in a collaborative mode, requiring data to be stored and delivered in a timely manner. This class of applications must adhere to stringent real-time constraints and Quality-of-Service (QoS) requirements. A QoS management approach is therefore required to orchestrate and guarantee the timely interaction between such applications and services. We discuss the design and a prototype implementation of a QoS system, and demonstrate how we enable Grid applications to become QoS compliant. We validate this approach through a case study of an image processing task derived from a nanoscale structures application.

Locating suitable services within a dynamic distributed system is a computationally intensive process, with no guarantee of quality and suitability of the discovered services. This is especially true for transient services, i.e. services which are likely to exist over short time frames. A significant effort has already been spent on developing distributed registry systems — such as the UDDI registry in Web services — to enable services to be published, and subsequently discovered. Regardless of the type of registry being used, it is nevertheless important to categorise services based on their particular properties — a process that should also aid the subsequent discovery of the service. A mechanism for grouping services based on a particular set of properties is investigated here — leading to the formation of service communities. Each such community is based on the existence of common parameter values being shared by members of the community. The structure of such a community is described, and a particular type of community established on the basis of Quality of Service properties is subsequently developed.

Some applications utilizing Grid computing infrastructure require the simultaneous allocation of resources, such as compute servers, networks, memory, disk storage and other specialized resources. Collaborative working and visualization are examples of such applications. In these applications, Quality of Service (QoS) is related to Grid services, and not just to the network connecting these services. With the emerging interest in “Service-Oriented Grids”, resources may be advertised and traded as services based on a Service Level Agreement (SLA). Such a SLA must include both general and technical specifications, including pricing policy and properties of the resources required to execute the service – to ensure QoS requirements are satisfied. A framework for QoS management is presented to enable Service-Oriented Grid users to specify, locate and execute Grid services with QoS constraints. The framework provides three particular features: 1) support for resource and service discovery based on QoS properties, 2) support for providing QoS guarantees at middleware and network level, and establishing SLAs to enforce these, and 3) providing QoS management on allocated resources based on a

The Universal Description, Discovery and Integration (UDDI) is a specification for distributed Web-based information registries for Web Services. UDDI allows HTTP-enabled business services to be published, and subsequently searched, based on their interface. UDDI consists of three components: "white pages" to hold basic contact information and identifiers for a company, "yellow pages" to enable companies to be listed based on their industry categories (using standard taxonomies), and "green pages" to record interface details of how a Web service is to be invoked. UDDI is however limited in scope - allowing white, yellow or green pages to be searched based on a few attributes, and does not provide an automatic mechanism for updating the registry as services (and service providers) change. We implement UDDIe -an extension to UDDI, which supports the notion of "blue pages", to record user defined properties associated with a service - and to enable discovery of services based on these. UDDIe enables a registry to be more dynamic, by allowing services to hold a lease - a time period describing how long a service description should remain in the registry. UDDIe can co-exist with existing UDDI - and has been implemented as open-source software.

In this paper the service abstraction is extended to support quality of service (QoS) attributes - and implemented in the Grid QoS Management (G-QoSM) framework. The framework supports three main functions: (1) providing mechanisms for establishing QoS guarantees via service level agreements (SLAs), (2) enabling QoS management on allocated QoS-aware services, and (3) supporting discovery of services based on QoS attributes. The framework relies on each service offering both a "functional" interface and a "management" interface. The functional interface provides attributes on how a service is to be invoked and how it returns results, whereas the management interface is used to provide QoS attributes and performance characteristics associated with a service. The focus of this paper is on implementing a QoS-based service discovery system, which utilises an extended version of the universal description, discovery and integration (UDDI) registry.

Some applications utilizing Grid computing infrastructure require the simultaneous allocation of resources, such as compute servers, networks, memory, disk storage and other specialized resources. Collaborative working and visualization is one example of such applications. In this context, Quality of Service (QoS) is related to Grid services, and not just to the network connecting these services. With the emerging interest in service-oriented Grids, resources may be advertised and traded as services based on a Service Level Agreement (SLA). Such a SLA must include both general and technical specifications, including pricing policy and properties of the resources required to execute the service – to ensure QoS requirements are satisfied. A QoS adaptation algorithm is presented to enable the dynamic adjustment of behavior of an application based on changes in the pre-defined SLA. The approach is particularly useful if workload or network traffic changes in unpredictable ways during an active session. The proposed QoS adaptation scheme is used to compensate for QoS degradation and optimize resource utilization, by increasing the number of requests managed over a particular time.

We extend the service abstraction in the Open Grid Services Architecture~\cite{ogsa} for Quality of Service (QoS) properties. The realization of QoS often requires mechanisms such as advance or on-demand reservation of resources, varying in type and implementation, and independently controlled and monitored. Foster et al. propose the GARA~\cite{FostKessl99} architecture. The GARA library provides a restricted representation scheme for encoding resource properties and the associated monitoring of Service Level Agreements (SLAs). Our focus is on the application layer, whereby a given service may indicate the QoS properties it can offer, or where a~service may search for other services based on particular QoS properties.

Gridcomputingprovidestheinfrastructurenecessarytoaccessandusedis- tributedresourcesaspartofvirtualorganizations.Whenusedinthisway,Grid computingmakesitpossibleforuserstoparticipateincollaborativeanddistributed applicationssuchastele-immersion,visualization,andcomputationalsimulation. Someoftheseapplicationsoperateinacollaborativemode,requiringdatatobe storedanddeliveredinatimelymanner.Thisclassofapplicationsmustadhereto stringentreal-timeconstraintsandQuality-of-Service(QoS)requirements.AQoS managementapproachisthereforerequiredtoorchestrateandguaranteethetimely interactionbetweensuchapplicationsandservices.Wediscussthedesignanda prototypeimplementationofaQoSsystem,anddemonstratehowweenableGrid applicationstobecomeQoScompliant.Wevalidatethisapproachthroughacase studyofanimageprocessingtaskderivedfromananoscalestructuresapplication.