In this paper we partially present an initial version of an Ontology Pattern Language, called S-OPL, describing the core conceptualization of serv- ices as a network of interconnected ontology modeling patterns. S-OPL builds on a commitment-based core ontology for services (UFO-S) and has been developed to support the engineering of ontologies involving services in different domains. S-OPL patterns address problems related to the distinction of general kinds of customers and providers, service offering, service negotiation and service delivery. In this paper, we focus on the first two. The use of S-OPL is demonstrated in a real case study in the domain of Information and Communication Technology services.