Persistent URL (PURL)
The Persistent Uniform Resource Locator (PURL) was developed and implemented by the OCLC as a naming and resolution service for general Internet resources. It is intended as an interim system to be used until the URN framework is well established. A PURL looks just like a URL, except it points to a resolution service instead of the actual location of the digital resource. The resolution service then redirects the user to the appropriate URL.