Support for change in RPDE3

RPDE3 is a framework for building environments. Great emphasis has been placed on supporting changes of various kinds, such as extensions to existing environments and creation of new environments by adapting existing environments. We have a three-pronged approach to supporting change: (1) use of a central framework providing key services is a uniform fashion, (2) an extended object-oriented programming paradigm supporting fine-grained changes by addition of small code fragments, and (3) structured representation of program material facilitating sophisticated language-sensitive processing. RPDE3 has been used on a daily basis for its own development for about three years now, and during that time has undergone extensive change. This experience has indicated strongly that our approach to supporting change is effective, and has identified extensions to it that should make it more effective still. This paper describes the approach and, primarily, our experience.