The Difference Creator Processor can be used to determine the intersection between a GeoEvent's geometry and a geofence and then clip or remove the portion of the geofence that intersects the GeoEvent's geometry.
The Difference Creator Processor requires two discrete geometries be specified. You cannot, for example, use a regular expression to specify several different geofences and remove the intersecting portions of each geofence from the GeoEvent's geometry. The processor also requires that the dimensionality of the geofence be equal to or greater than that of the GeoEvent's geometry—you cannot, for example, clip or subtract a point from a polyline (or a polyline from a polygon).
The Difference Creator Processor can be configured to replace the GeoEvent's geometry with the computed difference of the two geometries or place the difference into a new geometry field. Altering a GeoEvent's schema by adding a new field requires GeoEvent Server 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 Difference Creator Processor, see the Introduction to GeoEvent Server tutorial available from GeoEvent Server tutorials.