A method for assuring service grade with Assurance case: An experiment on a portal service

Current agreements on levels of portal services have some problems. For example, defined levels of services are not well validated with evidences. It is necessary to provide a way to show the evidence that the service satisfies the expected levels. In this paper, we propose a method to assure the levels of service based on Non Functional Requirements and Assurance case. Service levels are represented by NFR grade index value. Assurance case is used to validate the service satisfies the expected Index values.