1. A non-transitory computer-accessible memory medium that stores program instructions executable by a client computer to: establish a network connection with a server computer over a network; send a universal resource identifier (URI) to the server computer over the network, wherein the URI indicates a graphical program (GP) or a graphical program execution engine (GPEE), wherein the graphical program comprises a plurality of interconnected nodes or icons which visually indicate the functionality of the program, and wherein the interconnected nodes are graphical source code of the graphical program; and receive the GPEE from the server computer over the network in response to the URI, wherein the GPEE is executable in a web browser of a client computer to execute the graphical program in the web browser on the client computer; wherein the graphical program comprises a model of a physical system, and wherein the model of the physical system comprises two or more physical domains, and wherein execution of the graphical program models the physical system.