Editing Permalink (section)

==Purpose==
Permanence in links is desirable when content items are likely to be linked to, from, or [[citation|cited]] by a source outside the originating organization. Before the advent of large-scale dynamic [[website]]s built on [[database]]-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 [[Common Gateway Interface|Common Gateway Interface-based]] URLs are made more readable by simplifying them. The internal [[URI]] for a Wikipedia article named Example, which is <code><nowiki>http://en.wikipedia.org/w/index.php?title=Example</nowiki></code>, is generated via [[URL rewriting]] from the more human-readable external URL, <code><nowiki>http://en.wikipedia.org/wiki/Example</nowiki></code>.

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 Visitors who store the URL for a particular entry often find upon their return that the desired content has been replaced by something new.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]] 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]] or [[Atom (standard)|Atom]] syndication streams.

===Comparing with PURL===
Both ''permalink'' and [[PURL]] (persistent uniform resource locator) are used as a persistent URL, and redirect to the location of the requested [[web resource]]. The main differences in the concepts are about [[domain name]] and [[Time#List of units|time scale]]: PURL uses an independent dedicated domain name, and is intended to last for [[decade]]s; permalinks usually do not change the URL's domain, and are intended for use on timescales of years.