1. A computer-implemented method in a graphical modeling environment, the method comprising: providing a first control initiator, where the first control initiator is connected to a first subgraph by a first control signal, where: the control initiator is a block that uses a control signal output to explicitly control execution of one or more subgraphs; executing the first subgraph in a first thread whose execution is explicitly controlled; providing a second control initiator, where the second control initiator is connected to a second subgraph by a second control signal; executing the second subgraph in a second thread whose execution is explicitly controlled; and interacting with a data synchronization block, where: the interacting allows a result from the first subgraph to be used by the second subgraph when the second subgraph is executing, and the data synchronization block waits for the first thread to finish executing before allowing the first result to be used by the second subgraph when the second subgraph is executing.