Page Comparison

System components

There are the following types of clients components in a Bit Repository system:

Pillars

Pillars are responsable for maintaining copies of the store material and providing bit preservation related operations on these

There are the following types of pillars seen from the data perspective:

• A full copy pillar, which contains full copies of delivered files identified uniquely with a service level agreement
• A checksum pillar (with specific checksum type), which contains derived copies of delivered files, in form of a checksum. The checksums are identified uniquely with a service level agreement in the same way as for full copies pillars.

Clients

Clients which can be used to perform operations on the bit repository, e.g. PutFile, GetFile. See Functionality for a full listing.

Services

Services actively perform tasks without user triggering, see Reference services for examples of services.

Infrastructure

Provides the communication infrastructure for integrating the components. This consists of:

• An ActiveMQ Message Bus.
• A Monitoring Service 

Principles

The necessary information for clients, pillars and coordination layer is:

• Components have no direct knowledge of Pillars or Clients.
• The Pillars know how to communicate via the coordination layer, and can respond to messages according to definitions of certification and possible operations as specified in Service Level Agreements serviced by the pillar.

All need for specific knowledge of components in the system, e.g. physical location of pillars, must be avoided

• each others location. Communication is rather performed indirectly by using the specified Queues and topics.
• All communication is asynchronous.