Here’s a quick look at an example of SystemC code, you’re traditional NAND gate:

SC_MODULE(my_nand) {
sc_in a, b; sc_out f;

void run() {
f = !(a && b);

SC_CTOR(my_nand) {
sensitive }

It looks like some of hardware description languages I’ve seen such as Verilog. It lets you model inputs and outputs and a process here named run that takes the inputs a and b and does a nand to produce the output f. And it’s all continuous. The module will change the output value as the input values change.

The crazy thing is that this is C++ code. SystemC is a collection of header files that define the templated classes, such as sc_in, and some macros, such as SC_MODULE, as well as a runtime library that models the continuous nature of electronic signals and calls the process methods, such as run in our example, to execute the behaviors at the right time. Very cool use of C++ IMHO.

Now UML Action Semantics isn’t that much different than the behavior and structure modeled here. You have actions that have input pins and output pins and a behavior that runs when all the input pins are ready. All actions run in parallel. It’s a discrete event system as opposed to continuous, as software tends to be as opposed to hardware. But I wonder whether we can use C++ in a similar way to program action semantics.

With a runtime that uses the underlying OS threading system supporting multi-core systems to run the actions in parallel as much as possible and the familiarity of C++ and existing C++ tools, like the CDT :), but used to program a paradigm very different than traditional sequential C, it has me intrigued…