The header file which declares Kernel::String was moved to base, that means an include statement from MLDesigner 2, which read hinclude { "kernel/String.h" } would now read hinclude { "base/String.h" }.
You do not have to concern yourself with this change usually, the Update Version mechanism takes care of this.
Some of the built-in standard types used in Primitive programming were renamed to have a consistent naming scheme. This affects the types known from MLDesigner 2 as INT, FLOAT, STRING, COMPLEX, FIX, DATASTRUCT and CONTINUOUS.
These are now defined as INTTYPE, FLOATTYPE, STRINGTYPE, COMPLEXTYPE, FIXTYPE, DATASTRUCTTYPE and CONTINUOUSTYPE; thus, all built-in standard types end with TYPE now.
You do not have to concern yourself with this change usually, the Update Version mechanism takes care of this.
Now, resources use zero as lowest priority to store/serve transactions. In MLDesigner 2 zero was treated as highest priority. This change was made to have a priority handling consistent with that from the Queues models.