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A permalink or permanent link is a URL that is intended to remain unchanged for many years into the future, yielding a
hyperlink In computing, a hyperlink, or simply a link, is a digital reference to data that the user can follow or be guided by clicking or tapping. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text wit ...
that is less susceptible to
link rot Link rot (also called link death, link breaking, or reference rot) is the phenomenon of hyperlinks tending over time to cease to point to their originally targeted file, web page, or server due to that resource being relocated to a new address ...
. Permalinks are often rendered simply, that is, as
clean URL Clean URLs, also sometimes referred to as RESTful URLs, user-friendly URLs, pretty URLs or search engine-friendly URLs, are URLs intended to improve the usability and accessibility of a website or web service by being immediately and intuitively ...
s, to be easier to type and remember. Most modern blogging and content-syndication software systems support such links. Sometimes
URL shortening URL shortening is a technique on the World Wide Web in which a Uniform Resource Locator (URL) may be made substantially shorter and still direct to the required page. This is achieved by using a redirect which links to the web page that has a ...
is used to create them. A permalink is a type of
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, s ...
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 A content management system (CMS) is computer software used to manage the creation and modification of digital content (content management).''Managing Enterprise Content: A Unified Content Strategy''. Ann Rockley, Pamela Kostur, Steve Manning. New ...
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.


History

In the early years of the web, all content was static, and thus all
hyperlink In computing, a hyperlink, or simply a link, is a digital reference to data that the user can follow or be guided by clicking or tapping. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text wit ...
s pointed at a filename. Soon, though, many web pages became dynamic, and many URLs began to include query terms. One cited early use of the term ''permalink'' in its current sense was by
Jason Kottke Jason Kottke (born September 27, 1973) is an American blogger, graphic designer, and web designer known for his blog Kottke.org. He won a Lifetime Achievement Award as a blogger. , his blog is ranked #66 overall and #20 in Science on the Technor ...
on March 5, 2000, in a post titled: "Finally. Did you notice the".Finally. Did you notice the (kottke.org)
/ref>
Matt Haughey Matthew Haughey (born October 10, 1972) is an American programmer, web designer, and blogger best known as the founder of the community weblog MetaFilter, where he is known as ''mathowie''. Life and career Haughey grew up in Placentia, Califo ...
had discussed a permalink-style feature with
Blogger A blog (a truncation of "weblog") is a discussion or informational website published on the World Wide Web consisting of discrete, often informal diary-style text entries (posts). Posts are typically displayed in reverse chronological order s ...
co-founders Evan Williams and Paul Bausch the previous weekend, and Bausch had pointed out that it was technically feasible to produce permanent links in Blogger, using a feature (written by him) that allowed the ID of a post to be placed in a Blogger template. In response to Kottke's
blog A blog (a truncation of "weblog") is a discussion or informational website published on the World Wide Web consisting of discrete, often informal diary-style text entries (posts). Posts are typically displayed in reverse chronological order ...
, on March 6, 2000, Matt Haughey posted the technical details on his own weblog,Caroline wishes outloud for , A Whole Lotta Nothing
/ref> which helped open the way to widespread adoption.


Purpose

Permanence in links is desirable when content items are likely to be linked to, from, or
cited A citation is a reference to a source. More precisely, a citation is an abbreviated alphanumeric expression embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose of ...
by a source outside the originating organization. Before the advent of large-scale dynamic
website A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google Search, Google, Facebook, Amaz ...
s built on
database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...
-backed content management systems, it was more common for URLs of specific pieces of content to be static and human readable, as URL structure and naming were dictated by the entity creating that content. Increased volume of content and difficulty of management led to the rise of database-driven systems, and the resulting unwieldy and often-changing URLs necessitated deliberate policies with regard to URL design and link permanence. For example, Wikipedia's internal cgi-based URLs are made more readable by simplifying them. The internal
URI Uri may refer to: Places * Canton of Uri, a canton in Switzerland * Úri, a village and commune in Hungary * Uri, Iran, a village in East Azerbaijan Province * Uri, Jammu and Kashmir, a town in India * Uri (island), an island off Malakula Islan ...
for a Wikipedia article named Example, which is http://en.wikipedia.org/w/index.php?title=Example, is generated via
URL rewriting In web applications, a rewrite engine is a software component that performs rewriting on URLs (Uniform Resource Locators), modifying their appearance. This modification is called URL rewriting. It is a way of implementing URL mapping or routing ...
from the more human-readable external URL, http://en.wikipedia.org/wiki/Example. An entry in a blog with many entries is accessible from the site's front page for only a short time. Visitors who store the URL for a particular entry often find upon their return that the desired content has been replaced by something new. Prominently posting permalinks is a method employed by bloggers to encourage visitors to store a more long-lived URL (the permalink) for reference. Permalinks frequently consist of a string of characters that represent the date and time of posting, and an identifier that denotes the author who initially authored the item or its subject. Crucially, if an item is changed, renamed, or moved within the internal database, its permalink remains unaltered, as it functions as a
magic cookie In computing, a magic cookie, or just cookie for short, is a token or short packet of data passed between communicating programs. The cookie is often used to identify a particular event or as "handle, transaction ID, or other token of agreement b ...
that references an internal database identifier. If an item is deleted altogether, its permalink can frequently not be reused. Permalinks have subsequently been exploited for a number of innovations, including link tracing and link trackback in weblogs, and referring to specific weblog entries in
RSS RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...
or
Atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and ...
syndication streams.


Comparing with PURL

Both ''permalink'' and
PURL 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 H ...
(persistent uniform resource locator) are used as a persistent URL, and redirect to the location of the requested
web resource A web resource is any identifiable resource (digital, physical, or abstract) present on or connected to the World Wide Web.< ...
. The main differences in the concepts are about
domain name A domain name is a string that identifies a realm of administrative autonomy, authority or control within the Internet. Domain names are often used to identify services provided through the Internet, such as websites, email services and more. As ...
and time scale: PURL uses an independent dedicated domain name, and is intended to last for
decade A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years. Usage Any period of ten years is a "decade". For example, the statement that "du ...
s; permalinks usually do not change the URL's domain, and are intended for use on timescales of years.


Permalinks and versions

Many blogging and content management systems do not support versioning of content, that is, if an entry is updated, a uniquely accessible version is not created. Thus, in the context of these systems, a permalink may refer to different content over time. In the context of systems that support versioning, such as most
wiki A wiki ( ) is an online hypertext publication collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be either open to the pu ...
s, a permalink is commonly understood as a link to a ''specific version''. Here, both the link itself and the resource it refers to should not change over time.
MediaWiki MediaWiki is a free and open-source wiki software. It is used on Wikipedia and almost all other Wikimedia websites, including Wiktionary, Wikimedia Commons and Wikidata; these sites define a large part of the requirement set for MediaWiki ...
, the software that runs
Wikipedia Wikipedia is a multilingual free online encyclopedia written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and using a wiki-based editing system. Wikipedia is the largest and most-read refer ...
, supports this type of permanent link. In its current implementation, old versions of specific articles, images, and templates are referenceable by unique unchanging URLs, though current entries may not use old versions of images and templates. Permanent links to specific versions are recommended for citing articles from sources such as Wikipedia and
Wikinews Wikinews is a free-content news wiki and a project of the Wikimedia Foundation that works through collaborative journalism. Wikipedia cofounder Jimmy Wales has distinguished Wikinews from Wikipedia by saying, "On Wikinews, each story is to be ...
, to ensure that the content remains unchanged for review. A reviewer can then view the cited revision, the current revision, and the differences between the two.


Presentation

Blog entries are usually laid out as follows: *Title *Date *Body *Comments, permalink, and what category the entry was posted to (known as
metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...
) Permalinks are usually denoted by text link (i.e. "Permalink" or "Link to this Entry"), but sometimes a symbol may be used. The most common symbol used is the hash sign, or #. However, certain websites employ their own symbol to represent a permalink such as an
asterisk The asterisk ( ), from Late Latin , from Ancient Greek , ''asteriskos'', "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often voc ...
, a dash, a
pilcrow The pilcrow, ¶, is a handwritten or typographical character used to identify a paragraph. It is also called the paragraph mark (or sign or symbol), paraph, or blind P. The pilcrow may be used at the start of separate paragraphs or to ...
(¶), a
section sign The section sign, §, is a typographical character for referencing individually numbered sections of a document; it is frequently used when citing sections of a legal code. It is also known as the section symbol, section mark, double-s, or ...
(§), or a unique icon.


Permalink detection

Permalinks can be indicated within the
HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScri ...
of a page so as to allow automated browsing tools to detect the permalink and use it for linking instead of the stated URL. The link element should include the following attributes:


See also

*
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, s ...
*
Deep linking In the context of the World Wide Web, deep linking is the use of a hyperlink that links to a specific, generally searchable or indexed, piece of web content on a website (e.g. "http://example.com/path/page"), rather than the website's home page ( ...
*
Digital object identifier A digital object identifier (DOI) is a persistent identifier or handle used to uniquely identify various objects, standardized by the International Organization for Standardization (ISO). DOIs are an implementation of the Handle System; they a ...
(DOI) *
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 HT ...
(PURL) *
Uniform Resource Identifier A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...
(URI) *
URL mapping A web framework (WF) or web application framework (WAF) is a software framework that is designed to support the development of web applications including web services, web resources, and web APIs. Web frameworks provide a standard way to build and ...
*
Perma.cc Perma.cc is a web archiving service for legal and academic citations founded by the Harvard Library Innovation Lab in 2013. Concept Perma.cc was created in response to studies showing high incidences of link rot in both academic publications an ...


References


External links


Cool URIs don't change - Tim Berners Lee

Choose URIs wisely



cite-as: A Link Relation to Convey a Preferred URI for Referencing
{{Authority control Identifiers Unique identifiers ja:Uniform Resource Locator#パーマネントリンク