Uit ArchiMate:"A business service exposes the functionality of business roles or collaborations to their environment. This functionality is accessed through one or more business interfaces. A business service is realized by one or more business processes, business functions, or business interactions that are performed by the business roles or business collaborations, respectively. It may access business objects.
A business service should provide a unit of functionality that is meaningful from the point of view of the environment. It has a purpose, which states this utility. The environment includes the (behavior of) users from outside as well as inside the organization. Business services can be external, customer-facing services (e.g., a travel insurance service) or internal support services (e.g., a resource management service).
A business service is associated with a value. A business service may be used by a business process, business function, or business interaction. A business process, business function, or business interaction may realize a business service. A business interface or application interface may be assigned to a business service. A business service may access business objects. The name of a business service should preferably be a verb ending with '?ing'; e.g., 'transaction processing'. Also, a name explicitly containing the word 'service' may be used."