We investigate ambient services, which we define as services that are related to the surrounding physical environment of the user, are locally useful and can be considered a form of location-based services. We introduce the notion of service domain which refers to the geographical area of relevance and utility for ambient services. We also consider a stereotypical case where a user might be within multiple service domains at the same time (when the service domains containing the user overlap) and so, can utilize a collection of services comprising services selected from each of the service domains containing the user. A language of operators is given for defining such a collection of services in terms of constituent services from the overlapping service-domains. Moreover, we describe and evaluate a prototype system that shows how to compute the services for a user in multiple service domains. The result is a framework for reasoning about ambient services for filtering or proactively suggesting mobile services based on geographical boundaries.