Sort of a combination between topology and spatial joins... The idea is to create a spatial relationship between features. This relationship would be dynamic. For example if you have two feature classes: Market_Area (Polygon) and Customer (Point). Both features would have a common field, something like "Market Name". After the relationship is established, if you move the customer point from one market polygon to another the "Market Name" field would update dynamically.
Another example would be a point to line relationship where a line has a size and the point has a size, the point would inherit size from the line.
This type of relationship would have numerous applications and should be able to be related from point to line, point to polygon, line to polygon and even polygon to polygon.