Handle System

**Handle System Overview**:
– The Handle System is defined in RFCs 3650, 3651, and 3652 by the IETF.
– Handles consist of a prefix identifying a naming authority and a suffix for the local name of a resource.
– Prefixes are issued to naming authorities by MPAs upon payment of a fee.
– Naming authorities can create multiple handles with unique local names within their assigned prefixes.
– Handles are opaque, providing only the means to retrieve metadata about the resource.
– Handles are expressed as URIs through the info URI scheme.
– Handles are used in DOI and DSpace for scholarly and government documents.
– CNRI developed the system, which was later administered by the DONA Foundation.
– CNRI provides specifications and source code under a royalty-free Public License.
– Over 1000 handle services are operational, receiving 200 million resolution requests monthly.

**Handle System Functionality**:
– Local Handle Services consist of handle servers storing handle records and metadata.
– Handle servers communicate with other handle servers to resolve handles.
– Handles prevent link rot by not becoming invalid when metadata changes.
– Handles can be associated with multiple administrators and used in trust management applications.
– The identifier string is unique within the system and can have optional human-readable features.
– The resolution mechanism is reliable, scalable, flexible, trusted, and built on an open architecture.

**Comparison with URLs**:
– Handles are opaque and encode no information about the resource, unlike URLs.
– URLs encode attributes like server host names and file locations.
– Metadata linked to handles includes resource attributes and access types.
– Handles can resolve to different digital versions and business models.
– Handles are compatible with DNS but do not require it.
– Some Handle System namespaces have special presentation rules.

**Handle System Usage**:
– Handles identify various objects like journal articles and data sets.
– Handles are used in digital watermarking, GRID applications, and repositories.
– Thousands of handle services in 71 countries, with over 1000 in universities and libraries.
– Handles can be expressed as URLs using HTTP proxy servers.
– The system is widely adopted by public and private institutions.

**Global Handle Registry and Collaboration**:
– The Global Handle Registry stores information on naming authorities.
– Handle clients can be embedded in end-user or server software.
– CNRI collaborates with ITU on the use of the Handle System.
– Over 12,000 prefixes allow users to assign handles.
– Six top-level Global Handle Registry servers receive 68 million resolution requests per month.
– Proxy servers receive 200 million resolution requests per month.
– ITU listed the Handle System as an emerging trend in April 2009.