The increasing interest in service design implies the need for more formal approaches to the analysis, conceptualization, and implementation of services. In particular, this is critical when multiple actors, such as designers, developers, and managers are to apply a service design approach for a customer centric transformation of the organization and its service offerings. In this paper, we present key components of a formal language for the modelling of customer journeys. The language is developed, in particular, to support customer journey analysis and design; its formal character is meant to facilitate an unambiguous communication of a customer journey throughout a service organization, and to bridge the current gap between fuzzy front-end service design and service implementation. Application of the language is illustrated through case studies from a large web-based service provider and a power company.