Modifications to the definition of the service: Services evolve over time. Modifications or enhancements such as, adding additional operations or methods, adding resources, or modifying the existing capabilities of a service are performed on a service. These modifications may affect the existing consumers or the consumers may not be able to adopt the changes for some time and thus the need for versioning of a service with parallel existence of old and new version arises.

Modifications to policies enforced for a particular service: The policies enforced on a particular service can be changed or modified over a period of time. For example, in order to add new requirements of a new consumer, versioning can be useful to distinguish between the current and the new consumer requirements.