Any kind of launch validation is ultimately security related in some manner.
By having the separate <sev> element you can make the sub-elements depend on this parent element, since you can't expect other vendors to favour <cbitpos> which add burden to the documentation to make it clear. Of course, the price you pay for this is a more complex XML structure. <launch> <security> <sev> <sev_specific_elements/> </sev> </security>
This is not the way we usually do things - we wuld have a type="sev|..." which determines what child elements are permitted, as illustrated in the example above.
Oh, right. Also, having <sev> element wouldn't make it clear that you can only have one type active, either 'sev' or some other solution. Erik