A system and method for maintaining persistent object identifiers across versions of a collection of data. According to one embodiment of the present invention, a first collection of objects is compared to a second collection of objects. If an object in the first collection matches an object in the second collection, a reference is added to the object in the first collection referring to the object in the second collection, allowing the identifier to persist in both collections of objects. Additionally, according to one embodiment of the present invention, the data (or “facts”) associated with the object from the first collection are moved to the object from the second collection. In this way, data associated with matching objects is combined between two collections of objects while maintaining persistent object identifiers.