Program Chairs Message th The 4 International Service Availability Symposium (ISAS 2007) continued with the tradition of its predecessors by bringing together researchers and practitioners from both academia and industry to address the problems of service availability. The unique characteristic of a strong academic and industrial partnership was vividly - flected in this year s event, from the Organizing Committee to the contributions and the participants. Recognizing the value of broadening the scope of ISAS 2007, we included new topic areas that cover model-driven design and human factors....