Methodical restructuring of complex workflow activities

We describe a family of activity-split and activity-join operations with a notion of validity. The key idea of introducing the set of activity-split and activity-join operations is to allow users to restructure ongoing activities in anticipation of uncertainty so that any significant performance loss due to unexpected unavailablity or delay of shared resources can be avoided or reduced through release of early committed resources or transferring ownership of uncommitted resources. To guarantee the correctness of new activities generated by activity-split or activity-join operations, we define the notion of validity of activity restructuring operations and identify the cases where the correctness is ensured and the cases where activity-split or activity-join are illegal due to the inconsistency incurred