As opposed to centralized workflow management systems, the distributed execution of workflows can not rely on a trusted centralized point of coordination. As a result, basic security features including compliance of the overall sequence of workflow operations with the pre-defined workflow execution plan or traceability become critical issues that are yet to be addressed. Besides, the detection of security inconsistencies during the execution of a workflow usually implies the complete failure of the workflow although it may be possible in some situations to recover from the latter. In this paper, we present security solutions supporting the secure execution of distributed workflows. These mechanisms capitalize on onion encryption techniques and security policy models to assure the integrity of the distributed execution of workflows, to prevent business partners from being involved in a workflow instance forged by a malicious peer and to provide business partners identity traceability for sensitive workflow instances. Moreover, we specify how these security mechanisms can be combined with a transactional coordination framework to recover from faults that may be caught during their execution. The defined solutions can easily be integrated into distributed workflow management systems as our design is strongly coupled with the runtime specification of decentralized workflows.

Workflow technologies are becoming pervasive in that they enable the execution of business processes in distributed and ubiquitous computing environments. As long-running transactions, the execution of workflows in environments without dedicated infrastructures raises transactional requirements due to the dynamicity of resources available to run a workflow instance and the integration of relaxed atomicity constraints at both design and instantiation time. In this paper, we propose an adaptive transactional protocol for the pervasive workflow model developed in a previous work to support the execution of business processes in the pervasive setting. The execution of this protocol takes place in two phases. First, candidate business partners are assigned to tasks using an algorithm wherein the selection process is based on both functional and transactional requirements. The workflow execution further proceeds through a hierarchical coordination protocol managed by the workflow initiator and controlled based on a decision table computed as an outcome of the business partner assignment procedure. The resulting workflow execution is compliant with the defined consistency requirements, and the coordination decisions depend on the transactional characteristics offered by the partners assigned to each task. An implementation of our theoretical results relying on ontology Web Language for Series and Business Process Execution Language technologies is further detailed as a proof of concept.

Workflow technologies are becoming pervasive in that they enable the execution of business processes in distributed and ubiquitous computing environments. The execution of pervasive workflows raises transactional requirements due to their dynamicity and the need for relaxed atomicity. In this paper, we propose an adaptive transactional protocol for the pervasive workflow model developed in a previous work. The execution of this protocol takes place in two phases. First devices are assigned to tasks using an algorithm whereby workflow partners are selected based on functional and transactional requirements. The workflow execution further proceeds through a hierarchical coordination protocol managed by the workflow initiator and controlled based on a decision table computed as an outcome of the device assignment procedure. The resulting workflow execution is compliant with the defined consistency requirements and the coordination decisions depend on the transactional characteristics of the devices assigned to each task

Current Web services composition approaches do not take into account transactional requirements defined by designers. The transactional challenges raised by the composition of Web services are twofold: relaxed atomicity and dynamicity. In this paper, we propose a new process to automate the design of transactional composite Web services. Our solution enables the composition of Web services not only according to functional requirements but also to transactional ones defined using the acceptable termination states model. The resulting composite Web service is compliant with the consistency requirements expressed by designers and its execution can easily be coordinated using the coordination rules provided as an outcome of our approach

As opposed to existing workflow management systems, the distributed execution of workflows in pervasive environments can not rely on centralized control. The dynamic nature of the pervasive environments on the other hand does not allow a permanent assignment of roles to devices. In this paper, we suggest an architecture supporting distributed execution of workflows in pervasive environments based on a fully decentralized control and dynamic assignment of roles to devices. The architecture is defined in terms of data structures associated with the workflow execution plan and dynamic information, a protocol for the exchange of the workflow data among devices and a new function called role discovery dealing with the dynamic assignment of roles to devices. This architecture is applied in the context of Web services using BPEL as workflow description language