If you want the output of a form to always be in XSF format, you can set this format statically in the SAP Form Builder. However, you can overrule this setting from within the application program if required (see:Output Options).
If you want to usespool processing for XSF output, in the system at least one printer of type 'XSF' must be set up. SAP Smart Forms stores XSF in the spool in binary format to prevent information from being lost in conversions (see also: Output of XML Documents).
As long as you do not overrule the static setting from within the application program, SAP Smart Forms returns the form in XSF format when you call the generated function module.