One thing Í hear is "We can't change the xml schema, it's provided be our customer". That's a truth that can be bent.
As long as you use a copy of it, like in BizTalk, you can actually do whatever you like, it's not hardwired to the customer. You might not want to change sequence or structure, but it's often data types you do not agree upon.
So if the customer state it gonna be a date, and then sends 000000 if they don't have a date, change your copy of the schema to string and take care of it before sending it forward, as xs:nil or remove the element. Likewise another customer stated it would be a integer and then sends space if they didn't have a value. Change to string in your copy and take action.
This issue might most often occur in a flat file scenario, but some customers don't validate their xml before sending it.
I understand it demand some maintance if a new version of the schema is released, but I think it's worth it.
