(Requirement) Identifiers always refer to the same object
Identifiers are the fundamental mechanism for retrieving content from the DataONE system, and there is an expectation that an identifier will always refer to the same content.
In the case of data, the bytes of the retrieved object must always be the same, regardless of which node it is being retrieved from (checksum consistency).
In the case of science metadata, the behavior is not as precise. The original science metadata is always preserved (on a CN). The copies of science metadata distributed to Member Nodes may change depending on the functionality of the member node.
Data consistency is an important aspect of preservation and enhances the re-use of information.
Independently computed checksums of a randomly selected data object drawn from any nodes match the original value in the system metadata
Objects retrieved from a CN always match the system metadata checksum.