The Symmetric Difference Creator Processor can be used to clip or remove the intersecting portion of a GeoEvent's geometry and a geofence from the union of the two geometries. The symmetric difference of two geometries is essentially an exclusive OR statement.
The Symmetric Difference Creator Processor requires two discrete geometries be specified. You will not, for example, be able to use a regular expression to specify several different geofences and obtain a symmetric difference for the collection of geometries. The processor also requires geometries to have the same type—so you will not, for example, be able compute the symmetric difference between a point and a polyline as a union of the two.
The processor can be configured to replace the GeoEvent's geometry with the computed symmetric difference or place the symmetric difference into a new geometry field. Adding a new field to a GeoEvent alters the GeoEvent's schema, which requires GeoEvent Server to create a new GeoEvent Definition. The new GeoEvent Definition will be managed by GeoEvent Server and deleted if changes are made to the processor or the GeoEvent Service in which the processor participates.
For more information on the Symmetric Difference Creator Processor, see the Introduction to GeoEvent Server tutorial available from GeoEvent Server tutorials.