requirements-base

DPN requirements and assumptions
In the development of the system, legal and technical constraints have been imposed that change some assumptions, as originally conceived. 
Those changes do not affect the fundamental assumptions of the DPN concept.
DPN is dark, geographically and technologically diverse replication, with individual and centralized audit and succession.

"The intent of DPN remains the same. Build a system that ensures that deposited material remains available to future generations by architecting around single points of failure broadly conceived (i.e., technical failure, political failure, organizational failure, geographic failure)." 

•	DPN is a federated preservation network of independent preservation archives
  o	All archives act to preserve content, not just as remote storage.
•	DPN has agreements to allow for Succession of content in the event an archive can no longer perform its function as an archive.
  o	This is currently envisioned as a “Quit Claim” framework
  o	Based on input from the legal team, comprised from the Node institutions, we will update recommendations
  o	The successor of content will take on the responsibilities of and become the Administrative Node for the failed archive
•	DPN, as much as possible, has independent preservation implementations at each node.
•	DPN communications follow best practices and use mutual authentication over secure channels.
•	DPN provides for replication of content from a Ingest Node to Replicating Nodes
  o	DPN provides recovery of lost content at any Node
  o	DPN core service keeps 3 copies of ingested objects
•	DPN provides a service model so that any of the Nodes can ascertain if their content is valid.
•	DPN enables centralized auditing
  o	Process audit at the DPN federation
  o	Process audit at the Node
  o	Audit trails for events
  o	DPN supports Content Fixity audit
•	DPN provides status reporting, activity, logging, traffic, volume, events, etc.
  o	Global (across federation)
  o	At the Node level
  o	Periodic Reporting 
  o	Significant event reporting, for example succession events, loss of content, etc.
•	DPN supports
  o	a DPN UUID (globally unique identifier for each bag deposited)
  o	a common lightweight wrapper (bag) for content transfer
  o	retention of  ingested content indefinitely
•	Content may be de-accessioned upon extenuating circumstances (e.g. court order)
  o	duplication of critical metadata in the 'registry' and also in the content bags
  o	durable and persistent communication methods to support unreliable networks and node failure
  o	a distributed model, assuming eventual consistency (CAP Theorem) for replication of content and registries
•	DPN content and services are distributed and federated.
•	DPN supports succession and brightening of content.
•	Implementations are de-coupled implementations and architecturally distinct, as practicable, but the communication methodology is shared, resilient, and redundant.
•	DPN objects are preserved by all Nodes and support DPN preservation functions.
•	DPN has decoupled inter-node communication channels for
  o	content transfer
  o	process control.
•	Communication between nodes is not dependent upon other nodes.