Reasonable Server Faces (RSF) is an open source web programming framework written in Java, developed at the Centre for Applied Research in Educational Technologies (CARET) at the University of Cambridge. RSF is built on the Spring framework, and allows views to be templated in pure XHTML, as well as other XML dialects. RSF takes responsibility for the entire request processing cycle through HTTP request decoding, maintaining a bean model, invoking actions, directing errors, interpreting results and rendering views. A principal aim of RSF is to facilitate designs where zero server state is held in between requests.
RSF is notable for its extremely lightweight component model, a request-scope Inversion of Control layer (RSAC) modelled on the Spring framework, and a pure HTML templating engine, IKAT.