Although services are developed, used, applied and intensively discussed in nowadays IT practice, the concept of an IT service has not yet been introduced. Services are IT artifacts that can be used by many users in different context at different points of time in different locations and serve a certain purpose. They provide the data and functionality at the best point of time, in the agreed format and quality for the right user with the right location and context. We generalize some of the introduced notions such as the REA framework (resource-event-agent) and introduce a framework for conceptual modeling of IT service systems that is based on the classical rhetorical frame introduced by Hermagoras of Temnos (Quis, quid, quando, ubi, cur, quem ad modum, quibus adminiculis (W7: Who, what, when, where, why, in what way, by what means)). Services are primarily characterized by W4: wherefore (end), whereof (source), wherewith (supporting means), and worthiness ((surplus) value). Additionally, the purpose can be characterized by answering the why, whereto, when, and for which reason W4 questions. The secondary characterization W14H is given by characterizing user or stakeholder (by whom, to whom, whichever), the application domain (wherein, where, for what, wherefrom, whence, what), the solution they are providing (how, why, whereto, when, for which reason), and the additional context (whereat, whereabout, whither, when).

service systems, conceptual modelling, IT service systems, Web-based services, classical rhetorical frame, Hermagoras of Temnos, conceptual model for services