The realization of ubiquitous networks brings new challenges to application development. In this kind of network, services and, more specifically web services, have been used to provide the functionality required by its users and applications. In such environments features like automatic service discovery and composition are of need. This paper reports the ongoing work towards an approach for dynamic service discovery and composition. This approach is based on modeling services as independent of concrete implementations. This abstraction allows applications and users to subscribe to a desired functionality and later, the supporting platform discovers the service or a composition of services to provide that functionality.