602:
appended to the target URL. For example, consider a PURL with a URL of http//purl.org/some/path/ with a target URL of http://example.com/another/path/. An attempt to perform an HTTP GET operation on the URL http//purl.org/some/path/and/some/more/data would result in a partial redirection to http://example.com/another/path/and/some/more/data. The concept of partial redirection allows hierarchies of Web-based resources to be addressed via PURLs without each resource requiring its own PURL. One PURL is sufficient to serve as a top-level node for a hierarchy on a single target server. The new PURL service uses the type "partial" to denote a PURL that performs partial redirection.
614:
the presumption that a resource with a changed location may have also changed content, thus invalidating fragments defined earlier. Bos suggested that fragments should be retained and passed through to target URLs during HTTP redirections resulting in 300 (Multiple Choice), 301 (Moved
Permanently), 302 (Found) or 303 (See Other) responses unless a designated target URL already includes a fragment identifier. If a fragment identifier is already present in a target URL, any fragment in the original URL should be abandoned. Bos' suggestion failed to navigate the IETF standards track and expired without further work. Dubost
309:
address, even though the resource in question may have moved. PURLs may be used by publishers to manage their own information space or by Web users to manage theirs; a PURL service is independent of the publisher of information. PURL services thus allow the management of hyperlink integrity. Hyperlink integrity is a design trade-off of the World Wide Web, but may be partially restored by allowing resource users or third parties to influence where and how a URL resolves.
340:
The next part, the PURL domain, is analogous to a resource path in a URL. The domain is a hierarchical information space that separates PURLs and allows for PURLs to have different maintainers. One or more designated maintainers may administer each PURL domain. Finally, the PURL name is the name of the PURL itself. The domain and name together constitute the PURL's "id".
332:. All persistent identification schemes provide unique identifiers for (possibly changing) virtual resources, but not all schemes provide curation opportunities. Curation of virtual resources has been defined as, "the active involvement of information professionals in the management, including the preservation, of digital data for future use."
613:
Partial redirection in the presence of a fragment identifier is problematic because two conflicting interpretations are possible. If a fragment is attached to a PURL of type "partial", it is unclear whether a PURL service should assume that the fragment has meaning on the target URL, or discard it in
312:
A simple PURL works by responding to an HTTP GET request by returning a response of type 302 (equivalent to the HTTP status code 302, meaning "Found"). The response contains an HTTP "Location" header, the value of which is a URL that the client should subsequently retrieve via a new HTTP GET request.
585:
A PURL of type "307" informs a user that the resource temporarily resides at a different URL from the norm. PURLs of types 404 and 410 note that the requested resource could not be found and suggests some information for why that was so. Support for the HTTP 307 (Temporary
Redirect), 404 (Not Found)
400:
The most common types of PURLs are named to coincide with the HTTP response code that they return. Not all HTTP response codes have equivalent PURL types and not all PURL servers implement all PURL types. Some HTTP response codes (e.g. 401, Unauthorized) have clear meanings in the context of an HTTP
339:
PURLs are themselves valid URLs, so their components must map to the URL specification. The scheme part tells a computer program, such as a Web browser, which protocol to use when resolving the address. The scheme used for PURLs is generally HTTP. The host part tells which PURL server to connect to.
308:
A URL is simply an address of a resource on the World Wide Web. A Persistent URL is an address on the World Wide Web that causes a redirection to another Web resource. If a Web resource changes location (and hence URL), a PURL pointing to it can be updated. A user of a PURL always uses the same Web
773:
OCLC and
Internet Archive today announced the results of a year-long cooperative effort to ensure the future sustainability of purl.org. The organizations have worked together to build a new sustainable service hosted by Internet Archive that will manage persistent URLs and sub-domain redirections
601:
The PURL service includes a concept known as partial redirection. If a request does not match a PURL exactly, the requested URL is checked to determine if some contiguous front portion of the PURL string matches a registered PURL. If so, a redirection occurs with the remainder of the requested URL
557:
A PURL of type "303" is used to direct a Web client to a resource that provides additional information regarding the resource they requested, without returning the resource itself. This subtlety is useful when the HTTP URI requested is used as an identifier for a physical or conceptual object that
335:
PURLs have been criticized for their need to resolve a URL, thus tying a PURL to a network location. Network locations have several vulnerabilities, such as Domain Name System registrations and host dependencies. A failure to resolve a PURL could lead to an ambiguous state: It would not be clear
541:
A PURL of type "chain" allows a PURL to redirect to another PURL in a manner identical to a 301 or 302 redirection, with the difference that a PURL server will handle the redirection internally for greater efficiency. This efficiency is useful when many redirections are possible; since some Web
537:
that the PURL should always be used to address the requested resource, not the final URI resolved. This is to allow continued resolution of the resource if the PURL changes. Some operators prefer to use PURLs of type 301 (indicating that the final URI should be addressed in future requests).
256:
resulting in the transfer of the resolver service and its administration interface to
Internet Archive. The service is supported on newly created software, separate from all previous implementations. The transfer re-enabled the ability to manage PURL definitions that had been disabled in the
589:
PURLs of types "404" and "410" are provided to assist administrators in marking PURLs that require repair. PURLs of these types allow for more efficient indications of resource identification failure when target resources have moved and a suitable replacement has not been identified.
545:
A PURL of type "200" is an "Active PURL", in which the PURL actively participates in the creation or aggregation of the metadata returned. An Active PURL includes some arbitrary computation to produce its output. Active PURLs have been implemented in PURLz 2.0 and The
621:
Starting with PURLz 1.0 series, the PURL service implements partial redirections inclusive of fragment identifiers by writing fragments onto target URLs in an attempt to comply with and avoid problematic and inconsistent behavior by browser vendors.
179:
PURL version numbers may be considered confusing. OCLC released versions 1 and 2 of the Apache-based source tree, initially in 1999 under the OCLC Research Public
License 1.0 License and later under the OCLC Research Public License 2.0 License
605:
Partial redirections at the level of a URL path do not violate common interpretations of the HTTP 1.1 specification. However, the handling of URL fragments across redirections has not been standardized and a consensus has not yet emerged.
532:
Most PURLs are so-called "simple PURLs", which provide a redirection to the desired resource. The HTTP status code, and hence of the PURL type, of a simple PURL is 302. The intent of a 302 PURL is to inform the Web client and
618:
resurrected Bos' suggestions in a W3C Note (not a standard, but guidance in the absence of a standard). Makers of Web clients such as browsers have "generally" failed to follow Bos' guidance.
550:. They may be used to gather runtime status reports, perform distributed queries or any other type of data collection where a persistent identifier is desired. Active PURLs act similar to a
401:
conversation but do not apply to the process of HTTP redirection. Three additional types of PURLs ("chain", "partial' and "clone") are given mnemonic names related to their functions.
1067:
547:
193:
760:
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cannot be represented as an information resource. PURLs of type 303 are used most often to redirect to metadata in a serialization format of the
593:
PURLs of type "clone" are used solely during PURL administration as a convenient method of copying an existing PURL record into a new PURL.
1072:
1082:
80:. Early on many of those other hosts used descendants of the original OCLC PURL system software. Eventually, however, the
610:
indicate a pointer to more specific information within a resource and are designated as following a # separator in URIs.
239:
1077:
129:
PURLs are used to curate the URL resolution process, thus solving the problem of transitory URIs in location-based
534:
1087:
708:
559:
189:
955:
257:
OCLC-hosted service for several months. The service hosted on
Internet Archive servers supports access via
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browsers will stop following redirections once a set limit is encountered (in an attempt to avoid loops).
50:
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whether the PURL failed to resolve because a network failure prevented it or because it did not exist.
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144:. The remainder of this article is about the OCLC's PURL system, proposed and implemented by
31:
757:"OCLC and Internet Archive work together to ensure future sustainability of Persistent URLs"
305:. PURLs allow third party control over both URL resolution and resource metadata provision.
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are used as permanent/persistent URL and redirect to the location of the requested
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956:"Handling of Fragment Identifiers in Redirected URLs, Expired Internet Draft"
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172:(the 'Z' came from the Zepheira name and was used to differentiate the PURL
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came to be generic and was used to designate any redirection service (named
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in 1995. The PURL system was implemented using a forked pre-1.0 release of
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usually does not change the URL's domain, and is designed to persist over
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domain name is independently changeable, and is designed to persist over
365:
361:
301:
The PURL concept allows for generalized URL curation of HTTP URIs on the
849:"Metadata Foundations for the Life Cycle Management of Software Systems"
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Other notable PURL resolvers include the US Government
Printing Office (
181:
130:
895:"Uniform Resource Identifier (URI): Generic Syntax, RFC 3986 (STD 66)"
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704:
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content. This use of the 303 HTTP status code is conformant with the
349:
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with its URL (to be redirected), and to update this redirection-URL;
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360:. Roughly speaking, they are the same. Their differences are about
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for virtual resources. Other persistent identifier schemes include
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ensure the persistence (e.g. by contract) of the root URL and the
468:
Redirect to a target URL with trailing path information appended
139:
1017:
249:, that may replace the old PURL-services and PURL-technologies.
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The PURL concept was developed by Stuart Weibel and Erik Jul at
851:. School of Information Technology and Electrical Engineering,
575:
719:
and others, they use directly or indirectly the PURL concept.
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and 410 (Gone) response codes are provided for completeness.
329:
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Berners-Lee, T.; Fielding, R.; Masinter, L. (January 2005).
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898:
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204:
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62:
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under contract to OCLC and the official website moved to
30:"PURL" redirects here. For other meanings of "purl", see
1027:
759:(Press release). Dublin, Ohio: OCLC. 27 September 2016.
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235:
209:
72:
Originally, PURLs were recognizable for being hosted at
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Free software programmed in Java (programming language)
749:
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On 27 September 2016 OCLC announced a cooperation with
164:. The software was modernized and extended in 2007 by
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provides means, to its user-community, to include new
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196:implemented PURLs as of its 1.0 release in 2012.
192:in 2010 but the release was never finalized. The
184:). Zepheira released PURLz 1.0 in 2007 under the
1044:
457:Redirect to another PURL within the same server
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207:from 1995 to September 2016 and was reached as
176:site from the PURL resolver operated by OCLC).
774:for purl.org, purl.com, purl.info and purl.net
1028:US Government Printing Office's PURL resolver
1018:Official website for The Callimachus Project
846:
343:
296:
27:OCLC-designed persistent identifier scheme
731:"PURLs to improve access to the Internet"
728:
980:
978:
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523:Copy the attributes of an existing PURL
14:
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1038:DPE/PURL Information and Resolver Site
986:"Common User Agent Problems, W3C Note"
820:
786:Yakel, E. (2007). "Digital Curation".
281:. OCLC now redirects DNS requests for
242:and has been in operation since 1997.
148:(the Online Computer Library Center).
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785:
962:Networking Working Group. 1999-06-30
763:from the original on 2 February 2023
182:http://opensource.org/licenses/oclc2
109:http://myPurlResolver.example/name22
490:Temporary redirect to a target URL
446:Simple redirection to a target URL
39:persistent uniform resource locator
24:
729:Weibel, Stuart; Jul, Erik (1995).
435:Moved permanently to a target URL
240:Federal Depository Library Program
25:
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1006:
847:Hyland-Wood, David (2008-07-01).
114:provides means to associate each
57:to the location of the requested
1023:Internet Archive's PURL resolver
245:The PURL concept is used in the
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424:Content created or aggregated
76:or other hostnames containing
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1:
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562:(RDF) and have relevance for
238:), which is operated for the
98:http://myPurlResolver.example
1073:Cross-platform free software
853:The University of Queensland
597:Redirection of URL fragments
576:Technical Architecture Group
316:PURLs implement one form of
188:. PURLz 2.0 was released in
49:(URL) (i.e., location-based
7:
1083:Internet software for Linux
821:Martin, Sean (2006-06-30).
788:OCLC Systems & Services
625:
186:Apache License, Version 2.0
133:like HTTP. Technically the
51:uniform resource identifier
10:
1104:
1013:Official website for PURLz
901:Networking Working Group.
322:Digital Object Identifiers
151:
29:
990:World Wide Web Consortium
827:World Wide Web Consortium
800:10.1108/10650750710831466
641:Digital Object Identifier
631:Implementation examples:
580:World Wide Web Consortium
554:in relational databases.
326:Life Sciences Identifiers
203:resolver was operated by
1033:persistent-identifier.de
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344:Comparing with permalink
92:has a "root URL" as the
53:or URI) that is used to
47:uniform resource locator
1078:History of the Internet
737:(November/December): 19
297:Principles of operation
1088:Unix Internet software
936:Cite journal requires
874:Cite journal requires
107:in the root URL (e.g.
680:Uniform Resource Name
635:Archival Resource Key
318:persistent identifier
32:Purl (disambiguation)
823:"LSID URN/URI Notes"
608:Fragment identifiers
236:http://purl.fdlp.gov
174:open-source software
548:Callimachus Project
493:Temporary Redirect
406:
194:Callimachus Project
438:Moved permanently
404:
162:Apache HTTP Server
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512:Permanently gone
501:Temporarily gone
135:string resolution
67:HTTP status codes
61:. PURLs redirect
16:(Redirected from
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994:. Retrieved
992:. 2001-02-06
964:. Retrieved
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929:cite journal
918:. Retrieved
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1058:Identifiers
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741:17 December
649:identifiers
568:linked data
405:PURL types
362:domain name
213:as well as
131:URI schemes
1047:Categories
996:2008-03-01
966:2008-03-01
920:2008-03-01
858:2011-01-05
833:2011-01-05
692:References
504:Not Found
482:See Other
366:time scale
142:resolution
88:) that:
717:Permalink
665:Permalink
374:permalink
350:permalink
330:INFO URIs
272:purl.info
125:services.
915:30973664
829:ESW Wiki
808:33219560
767:10 April
761:Archived
655:Link rot
626:See also
535:end user
465:Partial
324:(DOIs),
290:purl.org
278:purl.com
266:purl.net
260:purl.org
247:w3id.org
228:purl.com
222:purl.net
216:purl.org
166:Zepheira
94:resolver
74:purl.org
55:redirect
705:URN LEX
578:of the
389:decades
152:History
140:SEF URL
45:) is a
913:
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616:et al.
520:Clone
471:Found
460:Found
454:Chain
449:Found
275:, and
225:, and
911:S2CID
804:S2CID
682:(URN)
643:(DOI)
637:(ARK)
515:Gone
410:Type
396:Types
378:years
348:Both
105:names
960:IETF
942:help
899:IETF
880:help
769:2023
743:2021
711:and
660:OPAC
566:and
526:N/A
509:410
498:404
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476:303
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432:301
421:200
385:PURL
364:and
354:PURL
352:and
205:OCLC
201:HTTP
158:OCLC
146:OCLC
116:name
78:purl
63:HTTP
43:PURL
18:PURL
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796:doi
713:DOI
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427:OK
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380:.
180:(
41:(
34:.
20:)
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