Baseline Member Node Implementation Requirements¶
This document is in draft status, copied mostly verbatim from subversion at: https://repository.dataone.org/documents/Projects/cicore/operations/source/member_node_deployment
All Member Nodes, regardless of Tier, share the same baseline requirement of managing their object collection such that:
- All objects are identified by a globally unique identifier.
Identifiers provide the primary mechanism for users to access a specific item. Identifiers must conform to the DataONE persistent identifier specification.
2. The original bytes of submitted objects are always available using the original identifier.
To satisfy DataONE’s preservation policy, the content bound to an identifier does not change and is thus immutable. Organizations starting with systems that allow overwrites will need additional mechanisms to ensure access to older versions (via MN_Read.get())
- Content access policies are respected.
Tier 2 and higher nodes satisfy this requirement by implementing the API and following the functional requirements for access control implementation. By implication, Tier 1 nodes can only host and expose public objects.
- Updates are treated as a separate objects.
An update to an existing object causes creation of a new object and a new identifier, and the object being replaced is archived. (Archiving removes the object from the search index, but leaves it available via MN_Read.get(). The isObsoletedBy / obsoletes relationship is established in the system metadata of both objects to allow navigation through the version chain.)
- Voluntary deletes are handled as archive actions.
Objects published to DataONE are not deleted, but archived. This helps ensure DataONE’s preservation requirements are upheld. An archived object has its archived field set to true in its systemMetadata, and the object remains accessible by its identifier. This applies to all objects ever exposed through the DataONE API regardless of how the content is added to a Member Node. For example, if a Member Node manages their collection with external tools, the system should behave such that deleted content is treated as archived, rather than actually deleted.
6. Compulsory (or administrative) deletes, are coordinated and executed via the DataONE Coordinating Nodes.
These are true deletes where the content is removed from all nodes, and is done ONLY in cases when illegal or inappropriate content is discovered and needs to be removed. Because content may be replicated to other nodes, a Member Node performing a compulsory delete must notify DataONE of the action to ensure any replicas are also removed. Otherwise the content may remain discoverable and accessible at other nodes.
Note that the Tier 3 MN_Storage API implements requirements 4, 5, and 6, and exposes that functionality to authorized users. Tier 1 and 2 member nodes still implement the same functionality, however they do not expose the functionality through the DataONE MN_Storage API. Instead, creates, updates, and archives are handled through non-DataONE mechanisms.