[ewilliams]

I agree strongly. Years ago I taught GPSS from the "big red book" (the famous one by Thomas J. Schriber). Both GPSS and the book force the modeler to think carefully about what happens when there is a time tie (in those olden days, the GPSS clock assumed integer values only!). A thorough understanding of the Current and Future Events Chains was demonstrably and obviously vital to correct modeling then. Today it is still vital -- but not quite so obviously at superficial examination!