In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....
A blog is a type of website or part of a website supposed to be updated with new content from time to time. Blogs are usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in...
An Internet forum, or message board, is an online discussion site where people can hold conversations in the form of posted messages. They differ from chat rooms in that messages are at least temporarily archived...
entry after it has passed from the front page to the archives. Because a permalink remains unchanged indefinitely, it is less susceptible to link rot
Link rot
Link rot , also known as link death or link breaking is an informal term for the process by which, either on individual websites or the Internet in general, increasing numbers of links point to web pages, servers or other resources that have become permanently unavailable...
. Most modern weblogging and content-syndication software systems support such links. Other types of websites use the term permanent links, but the term permalink is most common within the blogosphere
Blogosphere
The blogosphere is made up of all blogs and their interconnections. The term implies that blogs exist together as a connected community or as a social network in which everyday authors can publish their opinions...
. Permalinks are often simply stated so as to be human-readable
Human-readable
A human-readable medium or human-readable format is a representation of data or information that can be naturally read by humans.In computing, human-readable data is often encoded as ASCII or Unicode text, rather than presented in a binary representation...
In computing, a hyperlink is a reference to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text with hyperlinks...
s were permalinks, as content was static. However, when many web pages became dynamic, this was often no longer the case. As a result, a natural desire arose to name the problem and popularize solutions.
One cited early use of the term permalink in its current sense was by Jason Kottke
Jason Kottke
Jason Kottke is an American blogger and former web designer currently living in New York City. He designed the Silkscreen typeface and has won a Lifetime Achievement Award as a blogger...
on March 5, 2000, in a post titled: "Finally. Did you notice the". Matt Haughey had discussed a permalink style feature with Blogger
Blogger (service)
Blogger is a blog-publishing service that allows private or multi-user blogs with time-stamped entries. It was created by Pyra Labs, which was bought by Google in 2003. Generally, the blogs are hosted by Google at a subdomain of blogspot.com. Up until May 1, 2010 Blogger allowed users to publish...
Evan Williams may refer to:* Evan Williams , Canadian actor* Evan Williams , entrepreneur, Blogger and Twitter co-founder* Evan Williams , Scottish football goalkeeper* Evan Williams , horse racing jockey and trainer...
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, on March 6, 2000, Matt Haughey posted the technical details on his own weblog, 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
Citation
Broadly, a citation is a reference to a published or unpublished source . More precisely, a citation is an abbreviated alphanumeric expression Broadly, a citation is a reference to a published or unpublished source (not always the original source). More precisely, a citation is an abbreviated...
by a source outside the originating organization. Before the advent of large-scale dynamic websites built on database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
A content management system is a system providing a collection of procedures used to manage work flow in a collaborative environment. These procedures can be manual or computer-based...
s, 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, e.g., http://en.wikipedia.org/w/index.php?title=Permalink, are re-written to a more human-readable form, http://en.wikipedia.org/wiki/Permalink (see Rewrite engine
Rewrite engine
A rewrite engine is software that modifies a web URL's appearance . Rewritten URLs are used to provide shorter and more relevant-looking links to web pages...
).
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 which represent the date and time of posting, and an identifier which 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
Magic cookie
A magic cookie or just cookie for short, is a token or short packet of data passed between communicating programs, where the data is typically not meaningful to the recipient program. The contents are opaque and not usually interpreted until the recipient passes the cookie data back to the sender...
which 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
TrackBack
A trackback is one of three types of linkback methods for Web authors to request notification when somebody links to one of their documents. This enables authors to keep track of who is linking to their articles...
in weblogs, and referring to specific weblog entries in RSS
RSS (file format)
RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
syndication streams
Permalinks and versions
Many blogging and content management systems do not support versioning
Revision control
Revision control, also known as version control and source control , is the management of changes to documents, programs, and other information stored as computer files. It is most commonly used in software development, where a team of people may change the same files...
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
Wiki
A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...
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.
One wiki implementation which supports this type of permalinks is MediaWiki
MediaWiki
MediaWiki is a popular free web-based wiki software application. Developed by the Wikimedia Foundation, it is used to run all of its projects, including Wikipedia, Wiktionary and Wikinews. Numerous other wikis around the world also use it to power their websites...
, the software which runs Wikipedia. In its current implementation, old revisions of specific articles, images, and templates are referenceable by unique unchanging URLs, although old versions of images and templates may not be utilized by current entries. Permanent links to specific versions are recommended for citing articles from sources such as Wikipedia
Wikipedia
Wikipedia is a free, web-based, collaborative, multilingual encyclopedia project supported by the non-profit Wikimedia Foundation. Its 20 million articles have been written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site,...
Wikinews is a free-content news source wiki and a project of the Wikimedia Foundation. The site works through collaborative journalism. Wikipedia co-founder Jimmy Wales has distinguished Wikinews from Wikipedia by saying "on Wikinews, each story is to be written as a news story as opposed to an...
, 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
Entry
Comments, permalink, and what category the entry was posted to (known as metadata)
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
Asterisk
An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...
The pilcrow , also called the paragraph mark, paragraph sign, paraph, alinea , or blind P, is a typographical character commonly used to denote individual paragraphs...
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
of a page so as to allow automated browsing tools to detect the permalink and use it for linking instead of the stated URL
Uniform Resource Locator
In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....
. The link element should include the following attributes:
On the World Wide Web, deep linking is making a hyperlink that points to a specific page or image on a website, instead of that website's main or home page. Such links are called deep links.-Example:...
A digital object identifier is a character string used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found...
A persistent uniform resource locator is a Uniform Resource Locator that is used to redirect to the location of the requested Web resource. PURLs redirect HTTP clients using HTTP status codes...
Purple Numbers is a suite of tools that allows one to address paragraphs of HTML content. It was originally conceived by Douglas Engelbart for his creation of hypertext. The concept was later implemented in PurpleWiki by Eugene Eric Kim and Chris Dent. The name comes from the faint, purple numbers...
In computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...
Many blogging and content management systems do not support versioning