A SQL statement where clause that stipulates a subset of features to be displayed. The definition expression string uses the SQL-92 where clause syntax ( The default value is an empty string, which will allow all annotation features in the data source to be used by the AnnotationLayer. Warning: Be sure to escape special characters in the expression string as required for your platform. The DATE keyword expects the date format yyyy-mm-dd and the TIMESTAMP keyword expects the time stamp format yyyy-mm-dd hh:mm:ss. For more information, see the ArcGIS Blog article