Grid computing facilitates the sharing and aggregation of heterogeneous and distributed resources, such as computing resources, data sources, instruments and application services. With the advent of grid technologies, scientists and engineers are building more and more complex applications to manage and process large data sets, and execute scientific experiments on distributed grid resources. Means of composition and executing distributed applications to form complex workflow are needed. Some efforts in the research of business workflow and Web services orchestration can be reused in grid workflow systems.
To provide reliable and predictable Grid services, Service Level Agreements (SLAs) are currently one of the major research topics in Grid Computing. SLAs define an explicit statement of expectations and obligations in a business relationship between provider and customer. Thus, SLAs should guarantee the desired and negotiated Quality of Service (QoS), which is a mandatory prerequisite for the Next Generation Grids.
In this thesis, we discuss how to meet users' requirements by establishing SLAs and how to provide the Grid workflow services in terms of the committed Quality of Service. A policy adjuster integrated grid workflow management system is proposed to provide SLA guaranteed Grid workflow executions. The main contributions include an improved workflow management system with SLA integrated XML-based workflow language, a policy adjuster mechanism comprised by a policy decision scheme, a completion estimation with similarity degree scheme, and a prototype implementation of this novel architecture based on PQRM system. Finally to evaluate our proposed system, we processed several experiments using a collaborative heart disease identification application in Physio-Grid to show the characteristics and advantages of our system to the existing workflow management system and PQRM system. Through the results, we can see that our system achieves optimized performances in different cases according to various users' intentions so that the SLAs of Grid workflow applications are guaranteed.
