No abstract

Large scale scientific applications are frequently modeled as a workflow that is executed under the control of a workflow management system. One crucial requirement is the validation of the generated results, e.g. the traceability of the experiment execution path. The automated tracking and storage of provenance information during workflow execution could satisfy this requirement.. To collect provenance data using the grid-enabled scientific workflow management system WS-VLAM, experimentations were made with two different implementations of the provenance concepts. The first one, adopts the Open Provenance Model (OPM) using the Provenance Layer Infrastructure for e-Science Resources (PLIER). The second one is the history-tracing XML (HisT). This paper describes how these two provenance models are integrated into WS-VLAM.

Currently, most workflow management systems in Grid environments provide push-oriented job distribution strategies, where jobs are explicitly delegated to resources. In those scenarios the dedicated resources execute submitted jobs according to the request of a workflow engine or Grid wide scheduler. This approach has various limitations, particularly if human interactions should be integrated in workflow execution. To support human interactions with the benefit of enabling inter organizational computation and community approaches, this poster paper proposes the idea of a pull-based task distribution strategy. Here, heterogeneous resources, including human interaction, should actively select tasks for execution from a central repository. This leads to special demands regarding security issues like access control. In the established push-based job execution the resources are responsible for granting access to workflows and job initiators. In general this is done by access control lists, where users are explicitly mapped to local accounts according to their policies. In the pullbased approach the resources actively apply for job executions by sending requests to a central task repository. This means that every resource has to be able to authenticate against the repository to be authorized for task execution. In other words the authorization is relocated from the resources to the repository. The poster paper introduces current work regarding to the mentioned security aspects in the pull-based approach within the scope of the project "HiX4AGWS".

Currently, most workflow management systems (WfMS) in Grid environments provide push-oriented task distribution strategies, where tasks are directly bound to suitable resources. In those scenarios the dedicated resources execute the submitted tasks according to the request of a WfMS or sometimes by support of a Meta-Scheduling service. This approach has specific problems, especially because of various conditions and constrains that have to be taken into account like local policies or the sites' autonomy. To deal with such issues, this paper takes a closer look to the task distribution strategies. The established Grid WfMSs essentially support control-flow and data perspectives. However, they neglect the resource perspective. This paper exposes the advantages to deal with this perspective and demonstrates its feasability by a prototype implementation that integrates the missing resource patterns into UNICORE.