Persistent Uniform Resource Locator
PURLs (Persistent Uniform Resource Locators) are Web addresses that act as permanent identifiers in the face of a dynamic and changing Web infrastructure. Instead of resolving directly to Web resources, PURLs provide a level of indirection that allows the underlying Web addresses of resources to change over time without negatively affecting systems that depend on them. This capability provides continuity of references to network resources that may migrate from machine to machine for business, social or technical reasons.
The PURL toolkit was strongly influenced by the active participation of OCLC's Office of Research in the early Internet Engineering Task Force (IETF) Uniform Resource Identifier (URI) working groups and Zepheira's participation at W3C in defining a Web Architecture for identifying and managing decentralized resources for supporting a variety of business and information management needs.