While creating the domain model, you may encounter various situations where behavior may not be related to any object specifically. These behaviors can be accommodated in service objects.

Service objects are a part of the domain layer that does not have any internal state. The sole purpose of service objects is to provide behavior to the domain that does not belong to a single entity or value object.

Ubiquitous language helps you to identify different objects, identities, or value objects with different attributes and behaviors during the process of domain modeling. During the course of creating the domain model, you may find different behaviors or methods that do not belong to any specific object. Such behaviors are important, and so cannot be neglected. Neither can you add them to entities or value objects. It would spoil the object to add behavior that does not belong to it. Keep in mind that behavior may impact on various objects. The use of object-oriented programming makes it possible to attach to some objects; these are known as services.

Services are an abstraction that sit one level above pods, acting as a director between individual pods and the outside world.

Services define a policy to access selected pods. Once this is done, pods in this service’s set can communicate freely until the policy to access is changed.

Services are also convenient when creating complex, interdependent programs as they set a single Domain Name Service (DNS) record for all pods within their service. Another part of the program, a deployment (see below), can then use this DNS name to access information from these pods without needing to know the IP addresses for each.

In other words, another part of the program can connect to this pod group through the shared DNS record without needing to track status or information of each pod.

Group based access allows for greater flexibility than individual access as pods can be added or removed from the service group without code revision.