When a queued transaction changes from one state to another, it can inform a configured notifier object of the change. A notifier object can be called by the Arbortext PE Request Manager each time a queued transaction changes from one state to another. Notifiers are configured in e3config.xml. A notifier accepts parameters that control its operation, as well as an optional TestSet to respond only to certain types of transaction states. A notifier can be configured to take an action based on a change in queued transaction state. These states can be specified in the notifier parameter com.arbortext.e3.target-states, described in Configuring a Notifier.