When business rules are used in a workflow, you can assign appropriate rule sets to an activity step. See About rules for additional information.
To specify rules for an activity step
CAUTION It is strongly recommended that you do not use Asynchronous Rules with OnSave option because a step which was previously locked will be automatically unlocked after the rule has been executed, which might cause unexpected behavior in your application. When a rule executes asynchronously, the work item is removed from its queue, put into the isi queue for execution by the vwisi process, and then returned to the original queue. During this procedure, it is not possible to retain the lock on the work object, so after the asynchronous rule executes, a work item that was previously locked will no longer be locked by the user. This issue does not apply for rules executed asynchronously Before Execution or After Completion of the step.