Irfan Ul Haq

Distributed Trust Management for Validating SLA Choreographies

For business workflow automation in a service-enriched environment such as a grid or a cloud, services scattered across heterogeneous Virtual Organizations (VOs) can be aggregated in a producer-consumer manner, building hierarchical structures of added value. In order to preserve the supply chain, the Service Level Agreements (SLAs) corresponding to the underlying choreography of services should also be incrementally aggregated. This cross-VO hierarchical SLA aggregation requires validation, for which a distributed trust system becomes a prerequisite. Elaborating our previous work on rule-based SLA validation, we propose a hybrid distributed trust model. This new model is based on Public Key Infrastructure (PKI) and reputation-based trust systems. It helps preventing SLA violations by identifying violation-prone services at service selection stage and actively contributes in breach management at the time of penalty enforcement.

Aggregation patterns of service level agreements

IT-based Service Markets require an enabling infrastructure to support Service Value Chains and service choreographies resulting from service composition scenarios. This will result into novel business models where services compose together hierarchically in a producer-consumer manner to form service chains of added value. Service Level Agreements (SLAs) are defined at various levels in such a hierarchy to ensure the expected quality of service for different stakeholders. Automation of service composition directly implies the aggregation of their corresponding SLAs. Aggregation of hierarchical SLAs leads to cross-enterprize business networks such as Virtual Enterprize Organizations (VEO), Extended Enterprizes and Value Networks. During the hierarchical aggregation of SLAs, certain SLA information pertaining to different stakeholders is meant to be restricted and can be only partially revealed to a subset of their business partners. Based on our notions of SLA Choreography and SLA-Views, we formally define an aggregation model to enable the automation of hierarchical aggregation of Service Level Agreements. The aggregation model leads to the discovery of various aggregation patterns in context with service composition and business collaboration.

Aggregating Hierarchical Service Level Agreements in Business Value Networks

Business scenarios such as Business Value Networks and Extended Enterprises pose new challenges for service choreographies across heterogeneous Virtual Organizations. In such scenarios, services compose together hierarchically in a producer-consumer manner to form service supply-chains of added value. Service Level Agreements (SLAs) are defined at various levels in this hierarchy to ensure the expected quality of service for different stakeholders. Automation of service composition directly implies the aggregation of their corresponding SLAs. But so far, the aggregation of SLAs has been treated only as a single layer process which is insufficient to complement the hierarchical aggregation of services. In this paper we elaborate on the requirement of a hierarchical aggregation of SLAs corresponding to service choreographies in Business Value Networks. During the hierarchical aggregation of SLAs, certain SLA information pertaining to different stakeholders is meant to be restricted and can be only partially revealed to a subset of their business partners. We introduce the concept of SLA-Views to protect such privacy concerns. We, then formalize the notion of SLA Choreography and define an aggregation model based on SLA-Views to enable the automation of hierarchical aggregation of Service Level Agreements. The aggregation model has been designed to comply with the WS-Agreement standard.

A Parallel Branch and Bound Algorithm for Workflow QoS Optimization

Automated composition and optimization of workflows in service-enriched environments is a challenging research area with strong implications in globally distributed systems such as Grid Computing and Cloud Computing. A workflow is composed of web services selected in accordance with user requirements. A strong formal realization of the problem is inevitable to ensure efficiency based on various interdependent parameters. We devise a mathematical model in order to map abstract workflows into concrete workflows satisfying user requirements represented by QoS parameters. Our model, which is based on the Multidimensional Multi-choice Knapsack Problem (MMKP), defines a happiness measure, that takes into account these requirements as well as the weights given to each requirement by the user. Then we develop a parallelizable branch and bound algorithm to maximize this happiness measure. We incorporate the Kepler Workflow tool, CORBA and C++ based optimization components to simulate two versions of the algorithm: a sequential version and a parallel version. We also indicate how to use heuristics to reuse the results of the parallel optimization under dynamic changes in requirements or service availability. Finally, we show a speedup analysis of our implementation.

Grid Workflow Optimization Regarding Dynamically Changing Resources and Conditions

Automatic construction of workflows on the Grid currently is a hot research topic. The problems that have to be solved are manifold: How can existing services be integrated into a workflow, that is able to accomplish a specific task? How can an optimal workflow be constructed in respect to changing resource characteristics during the optimization process? How to cope with dynamically changing or incomplete knowledge of the goal function of the optimization process? - and finally: How to react to service failures during workflow execution? In this paper we propose a method to optimize a workflow based on a heuristic A * approach that allows to react to dynamics in the environment, as changes in the Grid infrastructure and in the users requirements during the optimization process and failing resources during execution.

Hierarchical aggregation of Service Level Agreements

IT-based Service Economy requires Service Markets to flourish for the trade of services. A market does not represent a simple buyer-seller relationship, rather it is the culmination point of a complex chain of stake-holders with a hierarchical integration of value along each point in the chain. To enable a Service Economy, Service Markets must be practically realized, which in turn requires an enabling infrastructure to support service value chains and service choreographies resulting from service composition scenarios. In such scenarios, services compose together hierarchically in a producer-consumer manner to form service supply-chains of added value. Service Level Agreements (SLAs) are defined at various levels in this hierarchy to ensure the expected quality of service for different stakeholders. Automation of service composition directly implies the aggregation of their corresponding SLAs. In this paper we elaborate on the requirements of hierarchical aggregation of SLAs corresponding to service choreographies leading to business models such as Business Value Networks. During the hierarchical aggregation of SLAs, certain SLA information pertaining to different stakeholders is meant to be restricted and can be only partially revealed to a subset of their business partners. We introduce the concept of SLA-Views to protect such privacy concerns. We then formalize the notion of SLA Choreography and define an aggregation model based on SLA-Views to enable the automation of hierarchical aggregation of Service Level Agreements. The aggregation model has been designed to comply with the WS-Agreement standard.

Rule-Based Workflow Validation of Hierarchical Service Level Agreements

Business-to-business workflow interoperation across Virtual Organisations (VOs)brings about possibilities for novel business scenarios. In such business scenarios, parts of workflows corresponding to different partners can be aggregated in a producer-consumer manner,making hierarchical structures of added value. Service Level Agreements (SLAs),which are contracts between service providers and service consumers, guarantee theexpected quality of service (QoS) to different stake holders at various levels inthis hierarchy. This hierarchical SLA choreography and aggregation poses newchallenges regarding its description, management, maintenance, validation, trust andsecurity. In this paper we focus on the design and assessment of an agent-enabled,rule-based validation framework for the hierarchical SLA aggregation, correspondingto cross-VO workflow cooperation.

SLA Validation of Service Value Chains

Business-to-Business (B2B) workflow/service interoperation across Virtual Organisations (VOs) brings about novel business scenarios. In these scenarios, parts of workflows (or services) corresponding to different partners can be aggregated in a producer-consumer manner, leading to hierarchical structures of added value interpreted as service value chains. Service Level Agreements (SLAs), which are contracts between service providers and service consumers, guarantee the expected quality of service (QoS) to different stakeholders at various levels of a service value chain. The essential requirements for such an SLA-based choreography of services include agile component-based infrastructure to support the corresponding choreography of their SLAs; proactive validation of SLAs to prevent violations; reactive validation of SLAs for penalty enforcement and breach management; and business enabling requirements such as trust, privacy, security and automation. In this paper we highlight the significance of these issues and propose their solutions. We then proceed to weave these solution components together into a comprehensive SLA validation framework that blends together two major systems: a rule based distributed system for SLA validation and a service monitoring system for the prevention of SLA violations.

Rule-based validation of SLA choreographies

For the Service Economy to prosper, IT-based Service Markets are required to perform certain business actions autonomically and autonomously, e.g., helping companies to establish networks of business relationships. Service Markets, to be practically realized require an enabling infrastructure that supports business-to-business (B2B) relationships among business stakeholders, resulting in value chains.B2B workflow interoperation across Virtual Organization (VOs) brings about novel business scenarios. In these scenarios, parts of workflows corresponding to different partners can be aggregated in a producer-consumer manner, leading to hierarchical structures of added value. Service Level Agreements (SLAs), which are contracts between service providers and service consumers, guarantee the expected quality of service (QoS) to different stakeholders at various levels along this hierarchy. Automation of service composition in these coalition workflows directly implies the aggregation of their corresponding SLAs. This hierarchical choreography and aggregation poses new challenges regarding SLA description, management, maintenance, validation, trust, and security. In this paper, we focus on design and architecture of an agent-oriented, rule-based validation framework for hierarchical SLA aggregation, enabling cross-VO workflow cooperation. The framework is based on the Rule Responder architecture, the RBSLA project, a formal model of SLA Views, and a distributed trust model.

Towards Dynamic Authentication in the Grid — Secure and Mobile Business Workflows Using GSet

Until now, the research community mainly focused on the technical aspects of Grid computing and neglected commercial issues. However, recently the community tends to accept that the success of the Grid is crucially based on commercial exploitation. In our vision Foster’s and Kesselman’s statement “The Grid is all about sharing.” has to be extended by “... and making money out of it!”. To allow for the realization of this vision the trust-worthyness of the underlying technology needs to be ensured. This can be achieved by the use of gSET (Gridified Secure Electronic Transaction) as a basic technology for trust management and secure accounting in the presented Grid based workflow. We present a framework, conceptually and technically, from the area of the Mobile-Grid, which justifies the Grid infrastructure as a viable platform to enable commercially successful business workflows.