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. We received a total of 25 submissions, each of which was thoroughly reviewed by at least three members of the Program Committee. Due to the limited time allocated for the symposium, many worthwhile manuscripts unfortunately did not make it into the final program. Our sincere thanks go to the Program Committee for conducting a vigorous review process in a rather tight time schedule. The detailed reviews and their generous comments have shaped the contributions into an excellent program.