I have use case that : "optIn Schema ", should have link to Recipient schema, where Recipient-Id will be foreign key in "optIn Schema ".
I have linked the schema in following way:
Please let me know how to resolve this.
You need to create an attribute with name recipientId inside your OptIn schema.
I can see that you have given the same . name to link element but as per your definition it will look for an attribute with same name.
Try to update the Xpath for the source with this expression and see if you still get the error