Permalink

From Academic Kids

A permalink (a portmanteau made by contracting the phrase "permanent link") is a type of URL designed to refer to a specific information item (often a news story or weblog item) and to remain unchanged permanently, or at least for a lengthy period of time to prevent link rot. The term was coined by Scott Banister and Matt Kerner in 1995, though the first implementation wasn't until March 2000 by Blogger co-founder Paul Bausch. Permanence in links is desirable when content items are likely to be linked to from, or cited by, a source outside the originating organisation, and are desirable even within organisations when the complexity of websites grows to more than a modest number of pages. In particular, the growth of extensive commercial websites built on database-backed content management systems necessitated deliberate policies with regard to URL design and link permanence.

In the case of static HTML pages, for example for a blog, there are no links to entries per se but to the page with the latest entries. If the author posts many entries, this can mean that a specific entry is only accessible for several days, if that. In that case, web users who have previously stored a URL which referred to a specific story, discover after some time that it has become invalid.

The same happens in professional websites which have migrated from internal URL schemes based on the directories in which static html data was stored to all-dynamic storage, where all the pages served arre generated on the fly by a database backed content management system.

Similarly, stories are sometimes given meaningless "magic cookie" names, and the (seemingly arbitrary) number used to generate these is often an internal database identifier integer. As articles are moved, deleted, and new articles created, the unique correspondence between articles and these database identifiers are lost, and again links can no longer be trusted to refer to the correct article after some time has passed.

Permalinks typically consist of a string of characters which represent the date and time of posting, and some (system dependent) identifier (which includes a base URL, and often identifies the author, subscriber, or department which initially authored the item). Crucially, if an item is changed, renamed, or moved, its permalink remains unaltered. If an item is deleted altogether, its permalink cannot 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 syndication streams.

Permalinks are supported in most modern weblogging and content syndicaton software systems, including Movable Type, LiveJournal, and Blogger.

Contents

Popular permalink formats

Authors of blogging software and websites which host users weblogs have not agreed on a standard format for permalink URLs. Indeed, they may never do so, as some feel that meta-information about an article should be obtained from the associated RSS stream or from <meta> tags in the content itself, and that URLs shouldn't be "cracked" to obtain this information. Consequently, although various permalink implementations accomplish essentially the same job, several vendors have produced different solutions.

Movable Type and typepad.com:

 http://<username>.typepad.com/<username>/<4 digit year>/<2 digit month>/<15 character name>.html

Blogspot:

 http://<username>.blogspot.com/<4 digit year>/<2 digit month>/<article name>.html

Wordpress:

 http://<site-specific prefix>/<4 digit year>/<2 digit month>/<2 digit date>/<article name>/

LiveJournal / bloglines:

 http://www.livejournal.com/users/<username>/<unique integer identifier>.html

Midgard CMS:

 http://<site-specific prefix>/midcom-permalink-<document unique identifier>

Formatting

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 represented by text (i.e. "Permalink" or "Link to this Entry"), but sometimes a symbol may be used. The most common symbol used is the pound sign, or #. However, certain websites may have a "trademark" symbol, such as an asterisk or dash. Sometimes, this trademark character is used as a permalink instead. Recently, it has also become acceptable for the entry's title to serve as the permalink.

PermaLink detection

PermaLinks can be displayed on the system using a HTML link element. This way authoring tools can automatically detect the PermaLink and use that for linking instead of the regular URL. The Link element should include two attributes:

<link rel="PermaLink" href="<PermaLink URL>" />

See also

External links

fr:Permalien

Used often in weblogs to keep sites up and running.

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