The double hyphen terminates the flags passed to a command. The curly braces only escape special characters in the
name of the datagroup--not in the names of the elements.
If your datagroup is listed as the first parameter for a command and the name of any datagroup starts with a hyphen, then you'd need to use the double hyphens. If it's the second parameter in the command, then it depend on whether the first parameter could have a leading hyphen.
It can't hurt to always use the double hyphens or curly braces for the datagroup name. But it's not necessary in most scenarios.
Aaron
Nimbostratus
