National Instruments BridgeVIEW - Manual (Page 334)

Appendix A HMI Function Reference
BridgeVIEW User Manual A-14 © National Instruments Corporation
error indicates that an error occurred when executing the Read Event
History VI. It was probably a problem with the group/tag name.
shutdown indicates that the BridgeVIEW Engine is shutting down. In this
case, the Read Event History VI returns immediately with shutdown
TRUE. You can use shutdown to exit any While Loop that calls the Read
Event History VI.
changed? is TRUE if a new alarm or event was read. If changed? is
FALSE, Read Event History probably timed out before the Event History
Display was updated.