(Work in Progress)

• Archival Unit (AU). An Archival Unit (AU) is a collection of related files (Artifacts). The LOCKSS audit and repair protocol operates on an AU at a time comparing the content of the AU between all nodes containing that AU. Thus, the primary purpose of AUs is to provide a way for nodes to agree on which files belong to an AU.

• • Traditional AUs collect files (Artifacts) from one or more websites, based on a start URL and crawl rules in the plugin.
• • Named AUs are more passive - Files must be stored in them by a REST client. Each Named AU must be assigned a handle (supplied by the network admin), which must be uniquely used for the AU across the PLN . It is essential that the same set of files in stored in each node on which the AU exists.

• AUID is a unique identifier for an Archival Unit; it's derived from the AU's defining characteristics.

• Artifacts are the individual files (plus metadata) that the system stores, audits & repairs, and serves/replays. They're named by a tuple: (namespace, AUID, URI, version). The URI may be any string; the version is an integer.

• Payload is the content stored in an artifact. In a plain file artifact it's the file content. In an HTTP response artifact it's the content not including the HTTP response headers.

• Namespaces allow multiple LOCKSS networks, or multiple LOCKSS nodes, to share a single repository, keeping their content separate. In a single node/single PLN environment the namespace argument to API calls may be omitted and will default to lockss.

• AuConfiguration ... Storing an AuConfiguration causes an AU to come into existence.

• Plugins are XML files which control the behavior of groups of related AUs. They are parameterized by the AuConfiguration. For traditional AUs they determine what to crawl, at what rate, how often, etc. NamedAUs by default use the NamedPlugin plugin, which prevents crawls and several other behaviors.