Adaptive Goals for Self-Adaptive Service Compositions

Service compositions need to continuously self- adapt to cope with unexpected failures. In this context adaptation becomes a fundamental requirement that must be elicited along with the other functional and non functional requirements. Beside modelling, effective adaptation also demands means to trigger it at runtime as soon as the actual behavior of the composition deviates from stated requirements. This paper extends traditional goal models with adaptive goals to support continuous adaptation. Goals become live, runtime entities whose satisfaction level is dynamically updated. Furthermore, boundary infringement triggers adaptation capabilities. The paper also provides a methodology to trace goals onto the underlying composition, assess goals satisfaction at runtime, and activate adaptation consequently. All the key elements are demonstrated on the definition of the process to control an advanced washing machine.