Self-Adaptive Management of Web Processes

Nowadays, we are assisting to a paradigmatic shift for the development of web applications due to the pervasive distribution of their components among a lot of servers, which are dynamically interconnected by web links. As a consequence, the application logic is often defined by exploiting workflow languages since they are more suitable to address the complexity of these new running environments. Moreover, in many business environments, the behaviour of a large-scale distributed web application is significantly influenced by context events, whose handling could require run-time adaptations of the application logic to properly react to the changing conditions of the execution context. This paper addresses the need for adaptation in large-scale web applications by proposing a programming paradigm based on “autonomic workflows”, i.e. workflows that are able to self-change their structure in order to allow for the continuation of the execution towards the termination, even if unexpected anomalies occur during the execution. The proposed approach exploits semantic languages for service description, autonomic managers driven by policies specified using a dedicated language, and a knowledge base containing information collected during processes execution. Autonomic actions are performed using Event Condition Action (ECA) rules for assessing system and process conditions, and a set of operations that allow for dynamic adaptation of the running processes. Furthermore, the correctness of workflow adaptation is checked before the modifications are performed, by using both syntactical and semantic constraints.