Any data that is extracted from an XFA designed form will be in an xml format. The question then becomes how to control the format of the data that is produced. By default the xml structure will follow that of the hierarchy (this is the use Fieldname binding or Normal binding). If you want the data to follow a particular structure (so that you can use it with other systems that have a defined format) then that is when you woudl use sample XML or a schema in the data connection. Then by binding nodes in the data connection to the fields, the form knows how to create the structure that you want. If structure is unimportant then simply stick with Normal bindings and no data connection is needed.
Hope that helps
Thanks for perfectly clear explanation Paul.
Is the concept the same with filling forms ? When using e.g. renderPDFForm, is it possible to just follow the Normal/default binding structer in xml-input variable and so to fill the form without creating xml-schema and binding the form fields with it?
(I did test with this and it does not work for me, but I probably have error in xpath).
Yes it is possible ...just beware that the engine probably expects an XDP format so the root level structure might be different than you expect.