Holds the persistent state of a workflow process instance. This interface
uses only standard Java data types; it does not need to know about
WAPI data types - conversions are handled externally to the persistence
service. No parameter validation need be performed by implementations.
author: Adrian Price See Also:ProcessInstanceAttributes
Returns the activity instance that started this process as a subflow.
The parent activity instance, or null if thisprocess instance does not have a parent.