"A SERVICE forms a natural part of a MODEL-DRIVEN DESIGN [and] has three characteristics..." #readingToday

A SERVICE forms a natural part of a MODEL-DRIVEN DESIGN. Declared in the model as a SERVICE, rather than as a phony object that doesn't actually represent anything, the standalone operation will not mislead anyone.

A SERVICE has three characteristics. 1. The operation relates to a domain concept that is not a natural part of an ENTITY or VALUE OBJECT. 2. The interface is defined in terms of other elements of the domain model. 3. The operation is stateless.

Domain-Driven Design, Eric Evans