A trust-based game theoretical model for Web services collaboration

We present in this paper a trust-based game theoretical model for Web services collaboration. Each collaboration is modeled as a game. In each round of the game, a collaborating Web service submits a cost for achieving a specific task. The task-owner Web service computes the so-called trust-based cost, which is the product between the submitted cost and the inverse of the trust value of the bidding Web service. The game winner is the Web service which has the minimal trust-based cost. The trust is derived from the quality attribute values of a Web service. These values are computed during a collaboration evaluation period. They are updated after each game round based on a demotion or promotion decision. We also show how the proposed model is convenient for modeling Web services composition and assessing the trust of composite Web services. Furthermore, we provide a metric for the assessment of the collaboration trust. The application of this metric shows that the use of the trust allows a safer collaboration with respect to a game where there is no consideration of the trust as a criteria for allocating tasks.