+Wherever possible, we ensure that all functional changes in MKWS are
+backwards-compatible, so that applications written against old versions of the
+toolkit will continue to work when running against newer versions.
+
+However, a few aspects of functionality unavoidably change in backwards
+incompatible ways. We ensure that **this only happens with new major
+versions** -- so it should _always_ be safe to upgrade to a new minor version.
+As an aid to porting old applications, we here note the specific
+backwards-incompatible changes in the various major releases, and those
+planned for future major releases.