We outline a specification style for reactive services that focuses on UML 2.0 collaborations and activities as reusable specification building blocks. In contrast to traditional component-based approaches, a collaboration directly describes the interactions between the components as well as the internal behavior necessary for a component to take part in it. To compose services from such reusable collaborations, we use events identified as input and output pins on the activities that are connected together. While our approach is formally settled in temporal logic, in this paper we focus on an example specification from the viewpoint of a service engineer.