View-based editing provides a technique to integrate program analysis tools into the comprehension and editing process. The programmer may study the result of an analysis in a separate view window and make changes in the output, and the system will propagate the changes back to the original program. In this paper, we will study how view-based editors and editable views can be made technically realizable and cognitively usable. The most important technical aspects are data flow considerations, the frequency of transformations, and the treatment of failures. For users, the most significant properties are understandability in the users? framework, avoidance of unexpected changes or side effects, and the smoothness of successive cycles.