What is a handle?
A handle is a persistent identifier, or persistent name, for a digital object regardless of where and how it is stored. It provides long-term access to a digital resource. Handles are assigned to full text publicly-releasable technical reports in portable document format (.pdf) available in DTIC Online Access Controlled.
What is a Uniform Resource Name (URN)?
URNs are persistent identifiers for information resources. RFC 1737 established a framework for URN requirements. Handles meet the requirements for URNs, which include:
The Handle System® is an implementation for URNs developed by the Corporation for National Research Initiatives (CNRI). It is a comprehensive system for assigning, managing, and resolving persistent identifiers for digital objects and other resources on the Internet. The Handle System® includes an open set of protocols, a namespace, and an implementation of the protocols. The protocols enable a computer system to store handles of digital resources in a distributed environment and resolve those handles into the information necessary to locate and access the resources. This associated information is changed as needed to reflect the current state of the identified resource without changing the handle, allowing the name of the item to persist over changes of location and other information. Combined with a centrally-administered naming authority registration service, the Handle System® provides a general purpose, distributed global naming service for the reliable management of information on networks over long periods of time. Details can be found at http://www.handle.net/.
A handle consists of two parts: a prefix - or "naming authority" - and a suffix - its local name (unique item ID). The naming authority and local name are separated by an "/". Top level naming authorities are registered by the Corporation for National Research Initiatives and are typically a publisher or an organization that manages information. These naming authorities identify the local handle service responsible for the handle and is globally unique and persistent. DTIC's naming authority is 100, and it has assigned 100.2 to current production. Because naming authorities are hierarchical, DTIC® can delegate naming privileges by creating sub-naming authorities to DoD publishers who want to create handles for their own products and be part of DTIC's Handle Service. A handle can be comprised of alpha or numeric characters or a combination of both
Examples of Handle Syntax (Note that the prefix and the suffix are divided by an "/"):
Remember that a handle is an identifier that remains unchanged for the life of the digital object to which it is assigned. For more details, see http://www.handle.net/overviews/handle-syntax.html or http://lcweb2.loc.gov/ammem/award/docs/h-s2.html.
The Uniform Resource Locator (URL) identifies the place an object is located. A handle is a name used to identify an object. A URL ties an Internet resource to its current network location and to its local file path. The problem is that, by definition, a location cannot serve as an identifier. When the resource is moved, the connection is severed and the URL link is broken. URLs must change when the object moves to another location. A useful analogy might be to equate a URL with a physical address where a person resides. If people are known solely by their address, when they move to another location there is no way to find them. They may leave a forwarding address, but eventually, forwarding addresses become unmanageable. However, if they are known by their name, it is easier to find them. The Handle System®, instead of identifying a file's location, assigns an identifier and stores information that can be updated to reflect its current location. No matter where the file is moved, you can use the handle to get to the information; the handle remains valid. To expand the analogy, if people register their addresses in a system like the Handle System®, and continue to update the address whenever they move, the they can always be located. An additional requirement is that the information be available for the 'long term'; i.e., it is kept online for a long period of time. Thus, the name is consistent, and it is persistent. This is the principal behind the Handle System®.
Web technology, by itself, does not yet recognize handles. Therefore, if you put a handle into a web browser, nothing will happen; the system will not know what to do with it. In handles parlance, the handle will not resolve. A proxy server understands handle protocol and transmits the handle to a proxy URL to resolve the handle. DTIC's proxy URL is http://handle.dtic.mil. Begin a handle with this address to retrieve a resource in a Web browser. Use of a proxy server/proxy URL provides additional benefits listed in the next FAQ.
Handles can be resolved in two ways: By use of a plug-in extension that enables browsers (Netscape and Internet Explorer Version 3+) to recognize the handle protocol and directly communicate with the Handle System® or by use of proxy servers that understand both the handle and http protocols. The former requires the plug-in be downloaded and installed on individual computer workstations; use of the proxy server requires no additional action on the part of the user. DTIC uses a proxy server to simplify and facilitate access to DoD resources. To retrieve data, add the proxy URL 'http://handle.dtic.mil' to each handle record. To resolve a handle from a browser window, put the proxy URL into the browser location with the handle (handle prefix + handle suffix). Example: http://handle.dtic.mil/100.2/ADA475594.
Handle resolution takes place in a distributed manner with interaction between the Global Handle Registry and local handle services. A handle is initially sent to the Global Handle Registry (which knows the location of each local handle service) where it is routed to the specific server that can resolve it. Each handle is associated with, and resolves to one or more pieces of typed data (usually a URL).
By using handles the researcher is assured that data on the Web will be preserved and electronically available for a long period of time. The goal is to preserve the information, ensure access to it and eliminate broken links.
The assignment of handles to DTIC's full text publicly releasable technical reports may have no meaning to researchers who accesses electronic documents through DTIC's Scientific and Technical Information Network (STINET) database; the fulltext is retrieved from the Technical Report (TR) Bibliographic database by a click. However, STINET resources do resolve through the Handle System®. A typical DTIC URL is very lengthy; access to DTIC documents from a Web browser outside the STINET system is much simpler using a handle which, used with the DTIC handle proxy server address, dramatically shortens the URL. An example of a handle embedded in the DTIC proxy URL is: http://handle.dtic.mil/100.2/ADA475594. Enter the DTIC proxy URL and the known handle (prefix + suffix) into any browser - and the full text is instantly retrieved. Long-term benefits include: Referencing an item is easier and the link remains accurate over time. Researchers can create a report that uses handles in the bibliography and, years later, enter the same handle references in a browser for instant access to the complete resource or redirection to updated information - with no more resultant dead links.
Handles are also a benefit for the producer/publisher. They are a way to preserve Internet-accessible electronic data in perpetuity, with access guaranteed regardless of local changes (e.g., changes from one server to another, changes in organizational name). However, handles are not magic. The handle always remains unchanged , but the data to which it resolves must be updated whenever local changes are made.
DTIC is committed to assigning handles to products with long-term value. With this commitment is an obligation to provide electronic access to "handle-enabled" resources for the 'long term". Handles for resources held on external servers will work as long as organizations are diligent in maintaining their accuracy.
There are a number of available guides to citing electronic resources. While there is no style guide for citing handles, it makes sense to combine rules where one rule does not quite fit. Bibliographic listings of electronic sources should follow the format of the style used for print sources. The Columbia Guide to Online Style recommends the following basic format for citing scientific electronic resources, which can be adapted to accommodate handles:
Author's Last Name, Initial(s)
Date of document
Title of document. Title of complete work [if applicable]
Edition or revision [if applicable]
Handle embedded in proxy URL <proxy URL forward slash/prefix forward slash/suffix>
Pedersen, Brian A. 14 Decemberl 2007. What Kept the Tank from Being the Decisive Weapon of World War One? <http://handle.dtic.mil/100.2/ADA475594>
(1 January 2008)
Organizations that contribute resources to DTIC are automatically part of the Handle Service program; contributed resources (limited for now to full-text .pdf resources that are identified as publicly releasable) are assigned handles as part of the routine steps in processing.
DTIC will manage and track handles for Department of Defense Web-accessible resources that participate in the Handle Service, and will provide direct links to these resources from the central directory, which is searchable from the handle search page. This database contains key information about the resources. When a search is conducted, a results list with the handle will be returned. A click on the handle will retrieve the resource. If search parameters match more than one entry, a multiple-entry results list will be displayed; the correct handle can be selected and the desired resource retrieved. All DoD resources belonging to organizations that participate in DTIC Handle Service are retrievable from the handle search. There is no charge for this service.
Handles, by themselves, do not describe the resources they identify. Without examining a resource itself, it is not possible to know what the associated handle is. This is the role of metadata - to find out what a resource is without having to inspect it; thus, metadata is important. To 'discover' what a handle is, you must know something about the resource. DTIC's metadata table provides 'kernel metadata' - very limited bits of data describing a resource. These key metadata elements make up the metadata database. The metadata database, housed in an Oracle database, is comprised of all metadata kernels for DoD resources that have handles and participate in DTIC's Handle Service.
Due to requirements levied by individual contributors, DTIC's Limited Document collection is available in Private STINET to registered users only. While unclassified, these documents are not publicly releasable without authorization and must be protected in accordance with controls assigned by the contributor. When limited documents are cited in an otherwise publicly releasable document, the entire document becomes subject to the limited distribution controls of the cited references and must be safeguarded. For additional information, see DoD Directive 5230.24, Distribution Statements on Technical Documents.