Overview and Structure of the Handle System
- Developed by Bob Kahn at the Corporation for National Research Initiatives (CNRI)
- Funded by the Defense Advanced Research Projects Agency (DARPA) between 1992 and 1996
- Handles are persistent identifiers assigned to information resources
- Handles are opaque and encode no information about the underlying resource
- Handles are bound only to metadata regarding the resource
- Handles consist of a prefix and a suffix
- Prefix identifies a naming authority
- Suffix gives the local name of a resource
- Prefixes are issued to naming authorities by multi-primary administrators
- Naming authorities can create multiple handles within their assigned prefixes
Implementation and Administration of the Handle System
- Defined in informational RFCs 3650, 3651, and 3652 of the Internet Engineering Task Force (IETF)
- Includes open protocols, a namespace, and a reference implementation
- Handles do not encode information about the underlying resource
- Metadata associated with the handle provides information about the resource
- Handles are resolved using a separate step called resolution
- CNRI administered and operated the Handle System until December 2015
- DONA Foundation now administers the Global Handle Registry
- Multi-primary administrators (MPAs) are accredited by the DONA Foundation
- Thousands of handle services are currently running
- Over 200 million resolution requests are received per month
Integration and Applications of the Handle System
- Provides the infrastructure for handle-based systems like Digital Object Identifiers (DOIs) and DSpace
- Used to provide access to scholarly, professional, and government documents
- CNRI provides specifications and source code for reference implementations
- Handles can be expressed as Uniform Resource Identifiers (URIs)
- Handle-based systems offer HTTP proxy servers for accessing handles
- Handles are used to identify journal articles, technical reports, books, theses, and more
- Handles are used in digital watermarking applications, GRID applications, and repositories
- Handles can resolve to different versions of the same content or different business models
- Thousands of handle services are running in 71 countries on 6 continents
- Major publishers use the Handle System for persistent identification of content
Design Principles and Handle Resolution Process
- Identifier string is not based on changeable attributes of the entity
- Identifier string is opaque and preferably a dumb number
- Identifier string is unique within the system
- Identifier string has optional features like being human-readable and embeddable
- Identifier resolution mechanism is reliable, scalable, flexible, trusted, and built on open architecture
- Handles are passed by a client as a query to the Global Handle Registry
- The Global Handle Registry responds with location information for the relevant Local Handle Service
- A query is then sent to the relevant server within the Local Handle Service
- The Local Handle Service returns the information needed to acquire the resource
- If the client already has information on the appropriate LHS, the initial query to GHR is omitted
Global Handle Registry and Related Technologies
- Global Handle Registry stores information on naming authorities within the Handle System
- Global Handle Registry can be queried to find out where specific handles are stored
- Global Handle Registry is a unique Local Handle Service within the distributed system
- Any local handle service can resolve any handle through the Global Resolver
- Global Handle Registry maintains and resolves the prefixes of locally maintained handle services
- The Handle System represents components of a long-term digital object architecture
- CNRI released the Digital Object Repository software, a major component of this architecture
- The release includes protocol specification, source code, and ready-to-use system, clients, and utilities
- The Handle System is used for persistent identification and resolution of digital objects
- It provides a framework for managing digital resources and ensuring their long-term accessibility
The Handle System is the Corporation for National Research Initiatives's proprietary registry assigning persistent identifiers, or handles, to information resources, and for resolving "those handles into the information necessary to locate, access, and otherwise make use of the resources".
As with handles used elsewhere in computing, Handle System handles are opaque, and encode no information about the underlying resource, being bound only to metadata regarding the resource. Consequently, the handles are not rendered invalid by changes to the metadata.
The system was developed by Bob Kahn at the Corporation for National Research Initiatives (CNRI). The original work was funded by the Defense Advanced Research Projects Agency (DARPA) between 1992 and 1996, as part of a wider framework for distributed digital object services, and was thus contemporaneous with the early deployment of the World Wide Web, with similar goals.
The Handle System was first implemented in autumn 1994, and was administered and operated by CNRI until December 2015, when a new "multi-primary administrator" (MPA) mode of operation was introduced. The DONA Foundation now administers the system's Global Handle Registry and accredits MPAs, including CNRI and the International DOI Foundation. The system currently provides the underlying infrastructure for such handle-based systems as Digital Object Identifiers and DSpace, which are mainly used to provide access to scholarly, professional and government documents and other information resources.
CNRI provides specifications and the source code for reference implementations for the servers and protocols used in the system under a royalty-free "Public License", similar to an open source license.
Thousands of handle services are currently running. Over 1000 of these are at universities and libraries, but they are also in operation at national laboratories, research groups, government agencies, and commercial enterprises, receiving over 200 million resolution requests per month.
