1. The operation performed by the Service refers to a domain concept which does not naturally belong to an Entity or Value Object.
2. The operation performed refers to other objects in the domain.
3. The operation is stateless

First and foremost, a service implies a client the requests of which the service is designed to satisfy. Another characteristic of a service operation is that of input and output - arguments and provided as input to an operation and a result is returned. Beyond this implication are usually assumptions of statelessness and the idea of pure fabrication according to GRASP.

From http://gorodinski.com/blog/2012/04/14/services-in-domain-driven-design-ddd/

Questions:

• Do services belong in Domain or Infrastructure? In this project there are services in the Domain section. Or could they simply be placed in the Domain folder if they represent a clear Domain concept?

  • Answer: According to this blog services belong in every part of the architecture, including domain. So domain can include services, but, distinctly:

  Domain services are different from infrastructural services because they embed and operate upon domain concepts and are part of the ubiquitous language.