ArcGIS for Desktop provides powerful methods for extending functionality and automating tasks to maximize productivity throughout the platform.
You can extend ArcGIS Server map and image services with custom logic.
Intercept requests for existing built-in operations of maps or image services executing custom logic and altering the behavior of these services in a way that is seamless to existing clients.
Create new service operations to extend the base functionality of map or image services. Most SOEs do this by using ArcObjects to work with GIS data and maps and provide the most flexibility in writing GIS functions.