This paper discusses models of generic mobile services. The goal is to gain understanding of the challenges in designing, developing and deploying advanced mobile data services. First, a composition model describing the components of a generic mobile service and the components relationships is given. Second, distribution models describing the distributions of the components in the former model across hosts, networks and domains are presented. After presenting these generic models, a brief mobility analysis is carried out, followed by a discussion of mobility and service continuity dependency on the service distribution. The functions necessary to provide service continuity are identified and incorporated in a service continuity layer.