As a model becomes more and more complex in Insight Maker, the number of connections between different components can start to become daunting. For complex models, Links and Flows may criss-cross each other in many places leading to a "spaghetti"-like model appearance that can be difficult to follow. Ghosting is one tool that can be used to combat this graphical complexity and to keep even the most complex models straightforward.
In short, ghosting allows you to make a reference to, or a Ghost of, a primitive in your model. The Ghost can be moved around in your model independently of the original primitive or its Source. This Ghost isn't a duplicate of the Source primitive (you don't now have two separate primitives) instead it is more of a mirror: it references the Source primitives value and state at all times. Any primitive that is connected to the Ghost primitive is automatically connect to the Ghost's Source and vice versa.
In Insight Maker, Ghosts of primitives are shown with a partially transparent graphical style. The above figure shows one example of a Ghosted primitive. If the Effect of EL LOS primitive had been connected directly to the EL LOS Product primitive, a Link would have to been made that cut across many other parts of the model. By using a Ghost of the primitive instead, we have achieved the same effect but the model diagram is now much cleaner.