PURR - The Persistent URL Resource Resolver

URLs have a precarious functional lifespan. They resolve the intended target (web page, PDF, audio stream, and so on) only so long as the target is available, otherwise they'll point to a dead end. Unfortunately, because companies fold, management changes, URL hostnames change, pages move, services are upgraded and reorganized, content becomes obsolete, and a host of other reasons, reliable, persistent URLs are the exception to the norm. We implemented PURR to provide persistent URLs to documents in our eprint archives. (See http://library.caltech.edu/digital).