REST allows client functionality to be extended by downloading and executing code in the form of applets or scripts. This simplifies clients by reducing the number of features required to be pre-implemented.—Roy Thomas Fielding and Richard N. Taylor. 2000. Architectural styles and the design of network-based software architectures. Ph.D. Dissertation. University of California, Irvine.

Code-On-Demand REST constraint. The Code-On-Demand constraint described by Roy Fielding in his ‘Architectural Styles and the Design of Network-based Software Architectures’ dissertation is interesting and something you don’t see applied in the wild.