The ''entity system'' is the infrastructure that runs the game's simulation/gameplay code. (The gameplay itself is not part of this system - the system is not even specific to RTS games - but it is all built on top of this system, and influences the system's design.)

The design is based most closely on the one presented in GPG5 (''Bjarne Rene: Component Based Object Management; Game Programming Gems 5, 2005, page 25''). Some other useful references: [http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/ Evolve Your Hierarchy], [http://www.gamearchitect.net/Articles/GameObjects1.html Game Object Structure: Inheritance vs. Aggregation], Scott Bilas's [http://www.drizzle.com/~scottb/gdc/game-objects.htm GDC 2002 presentation: A Data-Driven Game Object System], and a few of the things linked from those.