This example depicts the partitioning between the Classes Process Payment and Order Processor.
OMG UML Specification
The OMG UML specification (UML Superstructure Specification, v2.0, p. 12) states:
"A grouping of any set of model elements based on a set of criteria. 1. activity diagram: A grouping of activity nodes and edges. Partitions divide the nodes and edges to constrain and show a view of the contained nodes. Partitions can share contents. They often correspond to organizational units in a business model. They may be used to allocate characteristics or resources among the nodes of an activity."
The OMG UML specification (UML Superstructure Specification, v2.0, p. 307) also states:
"An activity partition is a kind of activity group for identifying actions that have some characteristic in common."