Onion: a Visual Formal Method for Workflow Design in Cloud Computing

This paper presents a new approach for workflow design in cloud computing. Generally the workflow design in cloud computing is specified by BPEL/BPMN, which is transformed into the existing formal methods for analysis and verification of the design. However the main paradigms of the existing methods reveal some limitations to the design due to their structural characteristics: process algebras mainly focus on in-the-large (ITL) views, and, reversely, state machines mainly focus on in-the-small (ITS) views. Therefore it is necessary to transform ITL views to ITS views, or vice versa, based on some equivalence relations. How can we avoid this notion of the equivalence and transformations to achieve some maximum integration views of the design? A new visual formal method, called Onion, is presented in this paper to integrate these two different ITL and ITS views in a single view. In Onion, processes and their transitive actions are graphically represented in one single entity, just like those of a real onion. Further the temporal properties of actions in the processes are specified in a geotemporal space. Once these are done, the requirements for the design are graphically specified on the processes and actions using a visual logic. Finally, the design is analyzed and verified through simulation in order to see whether it satisfies the requirements and restriction. The comparative study shows that the Onion approach is very effective and efficient for BPEL/BPMN and overcome some limitations of BPMN/BPMN. keywords: Cloud Computing, BPEL, BPMN, Onion, Geotemporal Space, Visual Logic, Analysis, Verification.