schema query

Imported from previous forum

Hello
I have certain queries with the FIXML v5 SP2 and am finding it tough to proceed without clarifying these doubts.
I would really appreciate any clarifications.

Certain fields are observed as mandatory in the Fiximate v5 SP2 but its been given as optional in the corresponding xsd.
For eg., SID, TID in the standard header are marked as mandatory in the fiximate specifications whereas its given as optional in the xsd.

And another question is in particular with the TradeCaptureReport (AE) message:

I find that there is a component for UndInstrmtGrp with the FIXML name as “Undly”, and its subcomponent name for the UnderlyingInstrument is also given as “Undly”. Is it fine?

Thanks in advance.

Karthik