1. A non-transitory computer accessible memory medium storing program instructions executable by a processor to: receive from a requesting program a request to determine an invocation interface of a graphical program, wherein the invocation interface is usable to invoke execution of the graphical program, wherein the graphical program is stored on a first computer system, wherein the requesting program executes on a second different computer system; programmatically determine the invocation interface of the graphical program in response to the request, wherein programmatically determining the invocation interface includes programmatically determining one or more parameters that should be passed to the graphical program when invoking execution of the graphical program, wherein said programmatically determining the one or more parameters includes programmatically determining default values of the one or more parameters; and return information specifying the invocation interface of the graphical program to the requesting program, wherein said returning includes returning information specifying the one or more parameters that should be passed to the graphical program, wherein the information specifying the one or more parameters includes information specifying the default values of the one or more parameters; wherein the information specifying the invocation interface of the graphical program is useable by the requesting program to invoke execution of the graphical program.