When unparsing xs:string data of specified length, then if the data is short then it is padded to the specified or minimum length (depends on dfdl:lengthKind). Whether to do this padding or not is controlled by the dfdl:textPadKind property, However we don't offer the same flexibility for xs:hexBinary. There's no controlling property, so we always output exactly what was in the infoset, and if specified length and the data is short it is a processing error. In the absence of a property to control whether to pad, would we better off always padding (using dfdl:fillByte) to specified or minimum length? Regards Steve Hanson Architect, Data Format Description Language (DFDL) Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh@uk.ibm.com tel:+44-1962-815848 Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU