General Information
The DOI® System uses the Handle System® to manage digital objects (see the DOI Factsheet "DOI System® and the Handle System®"). At the infrastructure level, DOI names are handles.
The DOI System Proxy Server is basically a web server that knows how to talk to the Handle System, and at this writing, most DOI names found on the web are embedded in URLs that use the proxy server for DOI name resolution. For any HTTP request that combines the proxy's domain name with a DOI name, for example
http://dx.doi.org/10.1000/demo_DOI
the proxy will query the Handle System for the DOI name, take the URL in the handle record (or if there are multiple URLs in the handle record it will select one, and that selection is in no particular order) and send an HTTP redirect to that URL to the user's web browser.
The proxy will return a specific URL if the query includes its unique index value, for example,
http://dx.doi.org/10.1000/demo_DOI?index=3
will redirect the user's web browser to the URL with index value 3.
Increasing numbers of DOI names include data in addition to the single default URL. This is sometimes referenced as multiple resolution. These added values are intended for use by more advanced applications which have the ability to take advantage of multiple pieces of data, e.g., the location of enhanced metadata or related documents. The proxy server, which is assumed to be talking to a plain web browser, ignores these values.
The proxy server is configured to display a "DOI Name Not Found" error page when queried for a DOI name that it cannot find.
The Handle System uses UTF-8, a Unicode implementation, and has no character set constraints. But the DOI System Proxy Server is a web server that sends redirects to web browsers using HTTP syntax, so characters in DOI names that may not be interpreted correctly by web browsers, for example '?', should be avoided or encoded. A non-ASCII character in a DOI name should be converted to UTF-8, and each UTF-8 byte that isn't ASCII should be %encoded.
The "# " is another example. Only if you send the DOI System Proxy Server the DOI name
10.1000/res#test
encoded as
http://dx.doi.org/10.1000/res%23test
will the proxy correctly resolve the DOI name. If it is not encoded, #test will be treated as a fragment and removed by the web browser before it gets to the proxy, which will then attempt to resolve 10.1000/res instead.
The DOI names
10.1000/demo_DOI and
10.1000/demo_DOI/ are both valid DOI names, but it is unlikely that a DOI name will be created with a trailing slash. If a resolution request for a DOI name with a trailing slash is received by the proxy server and that DOI name is not found, the proxy server will return an error report that includes a warning that the requested DOI name contained a trailing slash, and a link to click to resolve the same string without the slash.
The DOI System Proxy Server is really multiple servers running at multiple locations, with the load distributed evenly across all servers. To speed resolution, the proxy servers cache handle values, with the TTL set to 24 hours. This means that if a handle value is changed, it can take up to 24 hours before the new value is returned.
Documentation
Some additional functionality has been built into the DOI System Proxy Server to provide additional services for DOI System users. A collection of documentation for the additional functionality is being developed as a reference for users who structure their DOI names to use the DOI Proxy Server.
Additional References
- For general information on the proxy server, see the DOI Handbook chapter on Resolution.
- National Information Standards Organization. "ANSI/NISO Z39.84 - 2000 Syntax for the Digital Object Identifier", 24 pp., ISBN ISBN: 1-880124-47-5, ANSI Approval Date: 05/12/00. Available from NISO at http://www.niso.org/ and excerpted in Appendix 1 of the DOI Handbook.
