System and method for specifying and implementing programs. A graphical program is created in a graphical specification and constraint language that allows specification of a model of computation and explicit declaration of constraints in response to user input. The graphical program includes a specified model of computation, a plurality of interconnected functional blocks that visually indicate functionality of the graphical program in accordance with the specified model of computation, and specifications or constraints for the graphical program or at least one of the functional blocks in the graphical program. The specified model of computation and specifications or constraints are useable to analyze the graphical program or generate a program or simulation.