  In the context of dynamic evolution of workflow processes, the change region
identifies the part of the old process from which migration to the new process
is guaranteed to be inconsistent. However, this approach may lead to
overestimated regions, incorrectly identifying migratable instances as
non-migratable. This overestimation causes delays due to postponement of
immediate migration. The paper analyzes this overestimation problem on a class
of Petri nets models. Structural properties leading to conditions for minimal
change regions and overestimations are developed resulting into classification
of change regions into two types of change regions called Structural Change
Regions and Perfect Structural Change Regions. Necessary and sufficient
conditions for perfect regions are identified. The paper also discusses ways
for computing the same in terms of structural properties of the old and the new
processes.
