These formulas constrain a smaller rectangle to remain within a larger rectangle.
Constraints are quite useful in graphical interface technology.
They make the development of highly interactive interfaces easier for the applications programmer. For example, constraints can easily reconcile an application's state to its graphical presentation, and vice-versa. Dataflow constraints have proven a useful tool in this area. Currently, however, constraints are not used by most commercial software developers. Systems that use constraints tend to be much larger and slower than systems built with the traditional, but much more tedious, methods.