Maintaining Transactional Integrity in Long Running Workflow Services: A Policy-Driven Framework

Business to Business integration is enhanced by Workflow structures, which allow for aggregating web services as interconnected business tasks to achieve a business outcome. Business processes naturally involve long running activities, and require transactional behavior across them addressed through general management, failure handling and compensation mechanisms. Loose coupling and the asynchronous nature of Web Services make an LRT subject to a wider range of communication failures. Two basic requirements of transaction management models are reliability and consistency despite failures. This research presents a framework to provide autonomous handling of long running transactions, based on dependencies which are derived from the workflow. The framework presents a solution for forward recovery from errors and compensations automatically applied to executing instances of workflows. The failure handling mechanism is based on the propagation of failures through a recursive hierarchical structure of transaction components (nodes and execution paths). The management system of transactions (COMPMOD) is implemented as a reactive system controller, where system components change their states based on rules in response to triggering of execution events. One practical feature of the model is the distinction of vital and non-vital components, allowing the process designer to express the cruciality of activities in the workflow with respect to the business logic. A novel feature of this research is that the approach permits the workflow designer to specify additional compensation dependencies which will be enforced. A notable feature is the extensibility of the model that is eased by the simple and declarative based formalism. In our approach, the main concern is the provision of flexible and reliable underlying control flow mechanisms supported by management policies. The main idea for incorporating policies is to manage the static structure of the workflow, as well as handling arbitrary failure and compensation events. Thus, we introduce new techniques and architectures to support enterprise integration solutions that support the dynamics of business needs.