What makes PURLs “persistent”?
They never change. A PURL can be associated with any given resource/URL. While PURLs allow you to associate different URLs with them, the PURL itself never changes. Put another way, you can change what a PURL resolves to, but you can’t change the PURL. This means that a PURL can last longer than any particular URL that may be associated with it. PURLs persist indefinitely, and as long as they do, all instances of such PURLs (for example, links in a Web document or a bibliographic record) remain valid. Of course, someone has to operate the PURL resolvers that provide this persistence, and that’s the second source of persistence for PURLs. OCLC has long been committed to facilitating access to the world’s information, and that commitment stands behind PURLs, too. We encourage others who decide to operate PURL resolvers to provide the same level of commitment so the PURLs they resolve are truly persistent.
As long at the PURL resolver is functioning, the PURLs never change. A PURL can be associated with any given resource/URL. While PURLs allow you to associate different URLs with them, the PURL itself never changes. Put another way, you can change what a PURL resolves to, but you can’t change the PURL. This means that a PURL can last longer than any particular URL that may be associated with it. PURLs persist indefinitely, and as long as they do, all instances of such PURLs (for example, links in a Web document or a bibliographic record) remain valid.
