A map may have an active selection, which is a list of features on the map that have been selected and highlighted in the Viewer. The active selection is part of the run-time map state, and is not stored with the map resource in the repository.
The most direct method for creating an active selection is to use the interactive selection tools in the Viewer. Applications can also create selections using the Web API and apply them to a user’s view of the map. Any changes to the active selection require re-generation of the map image. Because of this, the Web server keeps information about the selection.