1. A computer program product comprising one or more computer-readable physical storage media having thereon computer-executable instructions which, when executed by one or more processors of a computing system, causes the computing system to perform a method for allowing declarative statements of constraints to govern how a visualization of a graphical model is validated, the graphical model comprising one or more objects that include interrelationships, at least some of the objects capable of being visualized on a display, the method comprising: identifying a graphical model that is to be subjected to the declarative constraint the graphical model including notation definitions that specify shapes, connectors, and decorators that are used to visualize objects and relationships of the graphical model; reading a declarative constraint that comprises one or more rules that the graphical model must adhere to in order to comply with the declarative constraint, the one or more rules specifying how the graphical model should function, and the one or more rules specifying properties, parameters, and relationships that objects of the graphical model should adhere to; interpreting the declarative constraint to identify or formulate underlying code that when executed causes the one or more rules associated with the declarative constraint to be checked against the identified graphical model; causing the computing system to execute the underlying code; and rendering on the display the results of checking the one or more rules against the identified graphical model.