I don't know the answer to the DFDL portion of your question, but I can say your two workarounds aren't equivalent. The latter will accept an initiator with no terminator, and vice versa (e.g., "{ data" and "data }", while the former will not. HTH, Jonathan From: dfdl-wg-bounces@ogf.org [mailto:dfdl-wg-bounces@ogf.org] On Behalf Of Garriss Jr., James P. Sent: Friday, March 08, 2013 12:42 PM To: dfdl-wg@ogf.org Subject: [DFDL-WG] Optional Initiator and Terminator? Is there a way to specify that an initiator/terminator pair is optional? IOW, these are both valid: { data } data If not, which of these workarounds is better (and why)? Choice DataWithInitiatorAndTeminator DataWithoutInitiatorAndTeminator Or Sequence OptionalInitiator (0 to 1) Data OptionalTerminator (0 to 1) These seem the same to me, but maybe there's a reason why one is better.