1. A computer-implemented method, comprising: receiving, by a local computing device, collection summaries for one or more data collections at a remote device, wherein a respective collection summary includes at least one additive hash value that represents one or more content items of a data collection; comparing, for a local data collection that also exists at the remote device, a local additive hash value for the local data collection with a remote additive hash value for the corresponding remote data collection at the remote device; and responsive to determining that the remote additive hash value does not match the local additive hash value, synchronizing structured names for the local data collection and the remote data collection at the remote device, wherein a structured name indicates a unique name for a content item independent of a storage location.