Filtering strings with Geoevent

[JasmineHunter1]

Hi,
I am trying to filter a definition for empty string values in a field called driverID. I have also tried filtering for a specific driverID that I know is in the data, as well as using double quotes instead of single quotes. I have also tried = and MATCHES with no luck. I have successfully filtered double and integer fields though. Does anyone have any suggestions for filtering strings?
Thanks,
Jasmine

[RyanJewett]

To filter for an empty string value, use the MATCHES operator with a value of ^$