Yes there is, I have seen them, and if you left them out, the county won't final the building. It's just like lateral bracing that goes along the bottom cords from end to end. They are on every engineered truss drawing that I have used. They prevent roll over in an earth quake. It's true that trusses are self supporting, but that doesn't mean bracing members aren't required to install them correctly. Your above information is a blanket statement and is absolutely incorrect.