In conjunction with ch.qos.logback.core.joran.action.PropertyAction sets the named variable to "true" if the file specified by path property exists, to "false" otherwise.
ch.qos.logback.core.joran.action.PropertyAction
path
In conjunction with ch.qos.logback.core.joran.action.PropertyAction sets the named variable to "true" if the resource specified by the user is available on the class path, "false" otherwise.
resource