A major advantage offered by Web services technologies is the ability to dynamically discover and invoke services. This ability is particularly important for operations of many applications executing in open dynamic environments. The QoS properties of the required and provided services play a significant role in dynamic discovery and invocation of services in open dynamic environments. In this paper, we discuss our approach to QoS specification and service provider selection, in the context of our work on the Dino project. The service provider selection algorithm used in Dino takes into account the relative benefit offered by a provider with respect to the requester-specified QoS criteria, and the trustworthiness of the provider. We explain our approach using an example from the automotive domain.