A good resource when examining trusses is the TPI truss installation guide found at Building Component Safety Information
click the view pdf link under the illustration of the cover. I've check it however, and it does not specifically discuss strapping or how the cap trusses are connected to the lower trusses. What I saw discussed was cont. lateral restraints and diagonal bracing. Anyway it is a useful source of information on truss installation do & don'ts.