Domain services for multichannel application software

Companies have to adapt to changing environments and business requirements in short cycles. They seek to address their customers via various channels involving new (net-based) technologies. This poses an interesting question: How can we support multiple channels with various user front ends without at the same time duplicating business functionality? We present an elegant solution in the form of an architectural approach based on so-called domain services. Domain services are related to core business functions or concepts and they abstract from any type of UI (user interface) or interaction style. Domain services also are independent of database systems, concrete work flows and technical prerequisites like host systems. When designing domain services, we focus on the tasks of an application domain because they are the most stable elements in enterprises. The core tasks of an enterprise remain the same as long as an organization stays in its business domain. However, the concrete work flows at the different workplaces and the (technical) front ends of the application systems will change. Consequently, it is important to identify the underlying tasks and model them as "faceless" services. Thus, one domain service can be combined with various channels, their user front ends and interaction styles may differ. Such a service may even be used by other software applications of business partners within the net of a virtual company. This paper discusses business-oriented as well as technical implications and solutions. We present our architectural design and concrete experiences gained from professional software projects.