Version 1.2 of the Workflow component that is part of the eZ Components adds support for the Cancel Case workflow pattern:

Cancel Case

As soon as a node of the ezcWorkflowNodeCancel type is activated, the complete workflow instance is removed. This includes currently executing nodes, those which may execute at some future time and all parent and sub-workflows. The workflow instance is recorded as having completed unsuccessfully.

My diploma thesis paper has been updated accordingly to reflect the addition of the ezcWorkflowNodeCancel class.