Persistent identifier

A persistent identifier (PI or PID) is a long-lasting reference to a document, file, web page, or other object.

The term "persistent identifier" is usually used in the context of digital objects that are accessible over the Internet. Typically, such an identifier is not only persistent but actionable:[1] you can plug it into a web browser and be taken to the identified source.

Of course, the issue of persistent identification predates the Internet. Over centuries, writers and scholars developed standards for citation of paper-based documents so that readers could reliably and efficiently find a source that a writer mentioned in a footnote or bibliography. After the Internet started to become an important source of information in the 1990s, the issue of citation standards became important in the online world as well. Studies have shown that within a few years of being cited, a significant percentage of web addresses go "dead,"[2][3] a process often called link rot. Using a persistent identifier can slow or stop this process.

An important aspect of persistent identifiers is that "persistence is purely a matter of service."[4] That means that persistent identifiers are only persistent to the degree that someone commits to resolving them for users. No identifier can be inherently persistent.

Persistent identifiers are often created within institutionally administered systems. These include:

However, some regular URLs (i.e. web addresses), maintained by the website owner, are intended to be long-lasting; these are often called permalinks.

Web archiving services such as,, and WebCite offer anyone the ability to archive a web page and create their own persistent identifier for it.


Other examples of PIDs include:


  1. ^ John A. Kunze, "Towards Electronic Persistence Using ARK Identifiers," section 3, California Digital Library [1]
  2. ^ Robert Sanderson, Mark Phillips, and Herbert Van de Sompel, "Analyzing the Persistence of Referenced Web Resources with Memento" (2011),
  3. ^ Bugeja, Michael (2010). Vanishing Act: The Erosion of Online Footnotes and Implications for Scholarship in the Digital Age. ISBN 978-1936117147.
  4. ^ Kunze, J. "The ARK Identifier Scheme".
  5. ^ "On constructing persistent identifiers with persistent resolution targets". IEEE Conference Publication. Retrieved 8 April 2018.

External links

Archival Resource Key

An Archival Resource Key (ARK) is a Uniform Resource Locator (URL) that is a multi-purpose persistent identifier for information objects of any type. An ARK contains the label ark: after the URL's hostname, which sets the expectation that, when submitted to a web browser, the URL terminated by '?' returns a brief metadata record, and the URL terminated by '??' returns metadata that includes a commitment statement from the current service provider. The ARK and its inflections ('?' and '??') provide access to three facets of a provider's ability to provide persistence.

Implicit in the design of the ARK scheme is that persistence is purely a matter of service and not a property of a naming syntax. Moreover, that a "persistent identifier" cannot be born persistent, but an identifier from any scheme may only be proved persistent over time. The inflections provide information with which to judge an identifier's likelihood of persistence.

ARKs can be maintained and resolved locally using open source software such as Noid (Nice Opaque Identifiers) or via services such as EZID and the central N2T (Name-to-Thing) resolver.

Closed for Winter

Closed for Winter is a 2009 Australian drama film starring Natalie Imbruglia.

It is based on Georgia Blain's critically acclaimed novel of the same title. The film was produced by Goalpost Pictures.


The Dataverse is an open source web application to share, preserve, cite, explore and analyze research data. Researchers, data authors, publishers, data distributors, and affiliated institutions all receive appropriate credit via a data citation with a persistent identifier (e.g., DOI, or Handle).

A Dataverse repository hosts multiple dataverses. Each dataverse contains dataset(s) or other dataverses, and each dataset contains descriptive metadata and data files (including documentation and code that accompany the data).

Digital object identifier

In computing, a Digital Object Identifier or DOI is a persistent identifier or handle used to identify objects uniquely, standardized by the International Organization for Standardization (ISO). An implementation of the Handle System, DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports and data sets, and official publications though they also have been used to identify other types of information resources, such as commercial videos.

A DOI aims to be "resolvable", usually to some form of access to the information object to which the DOI refers. This is achieved by binding the DOI to metadata about the object, such as a URL, indicating where the object can be found. Thus, by being actionable and interoperable, a DOI differs from identifiers such as ISBNs and ISRCs which aim only to identify their referents uniquely. The DOI system uses the indecs Content Model for representing metadata.

The DOI for a document remains fixed over the lifetime of the document, whereas its location and other metadata may change. Referring to an online document by its DOI is supposed to provide a more stable link than simply using its URL. But every time a URL changes, the publisher has to update the metadata for the DOI to link to the new URL. It is the publisher's responsibility to update the DOI database. If they fail to do so, the DOI resolves to a dead link leaving the DOI useless.

The developer and administrator of the DOI system is the International DOI Foundation (IDF), which introduced it in 2000. Organizations that meet the contractual obligations of the DOI system and are willing to pay to become a member of the system can assign DOIs. The DOI system is implemented through a federation of registration agencies coordinated by the IDF. By late April 2011 more than 50 million DOI names had been assigned by some 4,000 organizations, and by April 2013 this number had grown to 85 million DOI names assigned through 9,500 organizations.

Emotion (journal)

Emotion is a peer-reviewed scientific journal, which, as its title states, publishes articles relating to the study of emotion. It is one of several psychology journals published by the American Psychological Association. It was established by founding co-editors-in-chief Richard Davidson and Klaus Scherer in 2001. The current editor-in-chief is Paula R. Pietromonaco (University of Massachusetts). Initially published quarterly, the publication frequency has been bimonthly since 2008.

Enhanced publication

Enhanced publications or enhanced ebooks are a form of electronic publishing for the dissemination and sharing of research outcomes, whose first formal definition can be tracked back to 2009. As many forms of digital publications, they typically feature a unique identifier (possibly a persistent identifier) and descriptive metadata information. Unlike traditional digital publications (e.g. PDF article), enhanced publications are often tailored to serve specific scientific domains and are generally constituted by a set of interconnected parts corresponding to research assets of several kinds (e.g. datasets, videos, images, stylesheets, services, workflows, databases, presentations) and to textual descriptions of the research (e.g. papers, chapters, sections, tables). The nature and format of such parts and of the relationships between them, depends on the application domain and may largely vary from case to case.

The main motivations behind enhanced publications are to be found in the limitations of traditional scientific literature to describe the whole context and outcome of a research activity. Their goal is to move "beyond the simple PDF" (FORCE11 initiative) and support scientists with advanced ICT tools for sharing their research more comprehensively, without losing the narrative spirit of "the publication" as dissemination means. This trend is confirmed by the several enhanced publication systems devised in the literature, offering to research communities one or more of the following functionalities: Packaging of related research assets; Web 2.0 reading capabilities; Interlinking research outputs; Re-production and assessment of scientific experiments.

Handle System

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.


I-names are one form of an XRI — an OASIS open standard for digital identifiers designed for sharing resources and data across domains and applications. I-names are human readable XRIs intended to be as easy as possible for people to remember and use. For example, a personal i-name could be =Mary or =Mary.Jones. An organizational i-name could be @Acme or @Acme.Corporation.


i-numbers are a type of Internet identifier designed to solve the problem of how any web resource can have a persistent identity that never changes even when the web resource moves or changes its human-friendly name. For example, if a web page has an i-number, and links to that page use the i-number, then those links will not break even if the page is renamed, the website containing the page is completely reorganized, or the page is moved to another website.

Conceptually, an i-number is similar to an IP address, except i-numbers operate at a much higher level of abstraction in Internet addressing architecture. The other key difference is that i-numbers are persistent, i.e., once they are assigned to a resource, they are never reassigned. By contrast, IP addresses are constantly reassigned, e.g., your computer may have a different IP address every time it connects to the Internet.

Technically, an i-number is one form of an extensible resource identifier (XRI) — an abstract structured identifier standard developed at Organization for the Advancement of Structured Information Standards for sharing resources and data across domains and applications. The other form is called an i-name.

The i-number form of an XRI is designed to serve as an address that does not need to change no matter how often the location of a resource on (or off) the Internet changes. XRIs accomplish this by adding a third layer of abstract addressing over the existing layers: IP numbering (first layer) and DNS naming (second layer). The notion of a third layer for persistent addressing is not new — Uniform Resource Names (URNs) and other persistent identifier architectures have been developed for this purposes. However the XRI layer is the first architecture that combines a uniform syntax and resolution protocol for both persistent and reassignable identifiers.

At the XRI addressing layer, most resources will have both i-names and i-numbers. These different XRIs that all point to the same resource are called synonyms. I-name synonyms make it easy for humans to discover and address the resource, while i-number synonyms make it easy for machines to maintain a persistent identity for the resource. For example, if a company changes its name, it may register a new i-name and sell its old i-name to another company, however its i-number can remain the same — and links to the company that use its i-number won't break.

Furthermore, all of these forms of XRI synonyms can be resolved using the same http- or https-based resolution protocol. The results of XRI resolution are an XML document called an XRDS (Extensible Resource Descriptor Sequence). XRDS documents are the basis for the Yadis identity service discovery protocol that is now part of OpenID.

XRIs are also backwards compatible with the DNS and IP addressing systems, so it is possible for domain names and IP addresses to be used as i-names (or, in rare cases, as i-numbers). Like DNS names, XRIs can also be delegated, i.e., nested multiple levels deep, just like the directory names on a local computer file system. For example, a company can register a top-level (global) i-name and i-number for itself, and then assign second- or lower-level (community) i-names and i-numbers to its divisions, employees, etc.

International Geo Sample Number

The International Geo Sample Number or IGSN is a sample identification code of typically nine characters. As an active persistent identifier it can be resolved through the Handle System. The system is used in production by the System for Earth Sample Registration (SESAR), Geoscience Australia, Commonwealth Scientific and Industrial Research Organisation Mineral Resources, Australian Research Data Commons (ARDC), University of Bremen MARUM, and German Research Centre for Geosciences (GFZ). Other organisations are preparing the introduction of the IGSN.

The IGSN preserves the identity of a sample even as it is moved from lab to lab and as data appear in different publications, thus eliminating ambiguity that stems from similar names for samples from the earth. The IGSN unique identifier allows researchers to track the analytical history of a sample and build on previously collected data as new techniques are developed. Additionally, the IGSN provides a link between disparate data generated by different investigators and published in different scientific articles.

Link rot

Link rot (or linkrot) is the process by which hyperlinks on individual websites or the Internet in general tend to point to web pages, servers or other resources that have become permanently unavailable. There is no reliable data on how long web pages and other resources survive: the estimates vary dramatically between different studies, as well as between different sets of links on which these studies are based (see the #Prevalence section).

Numbering scheme

There are many different numbering schemes for assigning nominal numbers to entities. These generally require an agreed set of rules, or a central coordinator. The schemes can be considered to be examples of a primary key of a database management system table, whose table definitions require a database design.


Other numbering schemes are listed by field below.


A permalink or permanent link is a URL that is intended to remain unchanged for many years into the future, yielding a hyperlink that is less susceptible to link rot. Permalinks are often rendered simply, that is, as friendly URLs, so as to be easy for people to type and remember. Most modern blogging and content-syndication software systems support such links. Sometimes URL shortening is used to create them.

A permalink is a type of persistent identifier and the word permalink is sometimes used as a synonym of persistent identifier. More often, though, permalink is applied to persistent identifiers which are generated by a content management system for pages served by that system. This usage is especially common in the blogosphere. Such links are not maintained by an outside authority, and their persistence is dependent on the durability of the content management system itself.

Persistence (computer science)

In computer science, persistence refers to the characteristic of state that outlives the process that created it. This is achieved in practice by storing the state as data in computer data storage. Programs have to transfer data to and from storage devices and have to provide mappings from the native programming-language data structures to the storage device data structures.Picture editing programs or word processors, for example, achieve state persistence by saving their documents to files.


Persistent may refer to:

Persistent data

Persistent data structure

Persistent identifier

Persistent memory

Persistent Systems, a technology company

USS Persistent, three United States Navy ships

Persistent uniform resource locator

A persistent uniform resource locator (PURL) is a uniform resource locator (URL) (i.e., location-based uniform resource identifier or URI) that is used to redirect to the location of the requested web resource. PURLs redirect HTTP clients using HTTP status codes.

The PURL concept is generic and can be used to designate any redirection service (named PURL resolver) that:

has a "root URL" as the resolver reference (eg. http://myPurlResolver.example);

provides means, to its user-community, to include new names in the root URL (eg. http://myPurlResolver.example/name22);

provides means to associate each name with its URL (to be redirected), and to update this redirection-URL;

ensure the persistence (eg. by contract) of the root URL and the PURL resolver services.PURLs are used to curate the URL resolution process, thus solving the problem of transitory URIs in location-based URI schemes like HTTP. Technically the string resolution on PURL is like SEF URL resolution.

The remainder of this article is about the OCLC's PURL system, proposed and implemented by OCLC (the Online Computer Library Center).

Register (sociolinguistics)

In sociolinguistics, a register is a variety of language used for a particular purpose or in a particular communicative situation. For example, when speaking officially or in a public setting, an English speaker may be more likely to follow prescriptive norms for formal usage than in a casual setting; examples might include pronouncing words ending in -ing with a velar nasal instead of an alveolar nasal (e.g. "walking", not "walkin'"), choosing words that are considered more "formal" (such as father vs. dad, or child vs. kid), and refraining from using words considered nonstandard, such as ain't.

As with other types of language variation, there tends to be a spectrum of registers rather than a discrete set of obviously distinct varieties—numerous registers can be identified, with no clear boundaries between them. Discourse categorisation is a complex problem, and even in the general definition of "register" given above (language variation defined by use not user), there are cases where other kinds of language variation, such as regional or age dialect, overlap. Due to this complexity, scholarly consensus has not been reached for the definitions of terms such as "register", "field" or "tenor"; different scholars' definitions of these terms are often in direct contradiction of each other. Additional terms such as diatype, genre, text types, style, acrolect, mesolect, basilect, sociolect and ethnolect, among many others, may be used to cover the same or similar ground. Some prefer to restrict the domain of the term "register" to a specific vocabulary (Wardhaugh, 1986) (which one might commonly call slang, jargon, argot or cant), while others argue against the use of the term altogether. These various approaches with their own "register", or set of terms and meanings, fall under disciplines such as sociolinguistics, stylistics, pragmatics or systemic functional grammar.

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