A permanent ID is a value that will always represent the same entity, event, or concept. The ID remains valid even if the country changes its name, the street gets split into multiple segments. The ID will still point to the original concept.
As IDs are getting used by more and more data providers, multiple IDs may be discovered to represent the same concept, and should be merged. Yet, both IDs must remain, and point to the same concept.
Data publishers should always be aware of this feature of Cofactor IDs, and should try as much as possible to maintain ID continuity.
The Cofactor ID resolution service is available at http://cofactor.io. One needs to follow the Cofactor URI of the entity as it is referenced in semantic applications.
Note that you can use Cofactor Search to perform the reverse task—finding the Cofactor ID of an entity of interest.