Umlaut (software)
Umlaut is an open source front-end for a link resolver for libraries, which deals with advertising services for specific known citations. It runs as Ruby on Rails application via an engine gem. Umlaut accepts requests in OpenURL format, but has no knowledge base of its own, and is intended to be used as a front-end for an existing knowledge base. Currently only SFX is supported, but other plugins can be written.