Answer

Collections are at the core of Planview Hub. A collection defines the set of artifacts that are eligible to flow in an integration. 

Collections allow customers to scale their integrations in a couple different ways:

• They provide an easy mechanism to add additional projects to an integration, while taking advantage of existing field mappings.
• They can be easily plugged into a number of integrations; once a collection is mapped to a model, it can be plugged into an integration with any target collection that is mapped to the same model.

One fundamental aspect of a collection is that it’s comprised of one, and only one, artifact type. Whether they're stories, defects, requirements, or any number of other artifact types, each collection can only contain one artifact type. This facilitates better performance, more efficient change detection, and easier re-usability between integration components.

If an artifact type is changed after an artifact has been synchronized, it will no longer be a part of the original collection. This means that Hub will no longer be able to synchronize the artifact as part of that integration, and that artifact updates will no longer flow to the target repository.

Furthermore, if the new artifact type meets the criteria to be part of a different Hub collection, it could then synchronize as part of other integrations, potentially creating duplicate artifacts in other target repositories.