Research On Key Techniques Of Grid Semantic Workflow

It's the orientation of science research and business to congregate geographically distributed and heterogenous facilities and researchers as a virtual environment by using grid technology. Coordination and resource sharing are the main purposes of building grid systems, which can be partly realized with grid workflow. A workflow is a series of associated tasks linked together, which can be easily constructed, managed, monitored, and can execute automatically and efficiently in case submitted. Expanding scale and increasing resources induce intelligent resource inquiry and service composition as essential requirements, which are out of the ability of the conventional grid workflow. The thesis inducts semantic web and workflow technologies into grid, gives out the common concept of grid semantic workflow, constitutes the ontology-based workflow architecture, and studies annotation of semantic services, classification of semantic services, construction of grid workflow ontology model, automatic workflow composition, and time-cost optimization scheduling. The detail is as follows:Grid semantic workflow architecture. By analyzing the characteristics of semantic grid applications, the concept"grid semantic workflow"and a common architecture are given. According to the relation with lower resources, grid semantic workflow can be fractionized as abstract workflow, concrete workflow and executable workflow. Based on exsiting technologies and specifications of workflow, grid, semantic web etc., the architecture is constituted as a five layers structure composing of user layer, semantic workflow engine layer, semantic layer, web service layer and physical resource layer. The thesis lay emphasis on grid semantic resource management, including the annotation and classification mechanics of semantic services, and the weighing of Qos parameters for semantic services.Grid workflow ontology model. Ontology is an important expression of domain knowledge, and is the base to semantically describe resources. Aiming to the special demands of coordination and cooperation of grid application, the ontology framework is presented, which composes of domain ontology, organization ontology and service ontology, and OWL is used to define ontology concepts.Automatic creation of Qos-awared grid semantic workflow. Under dynamic grid environment, many uncertain factors affect the correctness, security and reliability of grid workflow strongly. A service composition algorithm is proposed, which considers user's IOPR requirements and Qos constraints jointly. Correlation vector of semantic services and a set of operations above it are used to represent service composition, and service composition is transferred as linear programming problem. An algorithm called IAFSSCM(Improved Artificial-Fish-School-Based Service Composition Method) is presented to solve service composition. A Qos weighing algorithm is introduced to evaluate user's Qos requirements, which uses Petri net as formalization tool. Simulation result demonstrates the method's affectivity.Semantic workflow scheduling. Aiming at the semantic Workflow scheduling with the objective of time-cost optimization, workflow is divided into segments according to its structure, and the deadline is partitioned to different segments. For tasks in each segment, their tasks are scheduled with Relative Time-Cost Rate algorithm. Simulative experiments show its performance improvement compared with other AI method.Grid workflow prototype and experiments. The prototype development is followed the architecture and research work introduced above. A simple simulated structural engineering experiment is demonstrated.