Supporting coordinated maintenance of system trustworthiness and user trust at runtime

In addition to design-time considerations, user trust and the trustworthiness of software-intensive socio-technical systems (STS) need to be maintained during runtime. Especially trust can only be monitored based on the actual usage of the system in operation. Service providers should be able to make informed decisions about runtime adaptation based on trust and trustworthiness, as well as respective essential relations. In this paper we present a unified approach to support the coordination of trust and trustworthiness maintenance. Trustworthiness maintenance is based on measuring objective system qualities, while trust maintenance considers two complementary measures of trust, i.e., the user behavior, and an estimation of the perceived system trustworthiness. A prototype tool demonstrates the feasibility of our approach. Furthermore, we illustrate specific functionalities of the tool by means of an application example