Persistent Uniform Resource Locator (PURL)

A uniform resource locator (URL) is a unique alphanumeric string that specifies where in a digital space an identified resource is located and the mechanism for retrieving it. A Persistent URL differs by not locating the resource directly, but by pointing the query to a more stable resource (e.g. a web domain rather than a web
page) before redirecting to the requested item. PURLs were created as a means of managing the apparently arbitrary disappearance of content from digital name spaces.