This is covered by section 9.3.2 (establishing representation) and section 9.5 (evaluation order). Your integer is not nillable, so can't have nil rep. Assuming compliance with dfdl:emptyValueDelimiterPolicy it therefore has empty representation. Assuming this is a local element with minOccurs-=1 implicitly, and no default value, it is a parsing error. Section 9.5 says the assert will never be executed as it is lower down the evaluation order. Regards Steve Hanson IBM Hybrid Integration, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 Note: I work Tuesday to Friday From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: DFDL-WG <dfdl-wg@ogf.org> Date: 19/03/2020 22:50 Subject: [EXTERNAL] [DFDL-WG] Clarification: zero-bit-long integer parses to value 0, or parse-error or? Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org> Consider: <xs:element name="spare" dfdl:length="{ $tns:WordPaddingBits }"> <xs:simpleType dfdl:lengthKind="explicit"> <xs:annotation> <xs:appinfo source="http://www.ogf.org/dfdl/"> <dfdl:assert test="{ . eq 0 }" /> </xs:appinfo> </xs:annotation> <xs:restriction base="xs:unsignedInt"> <xs:enumeration value="0" /> </xs:restriction> </xs:simpleType> </xs:element> Now, suppose the variable tns:WordPaddingBits has value 0. So this padding integer will be length 0 (this binary data with lengthUnits bits). Currently, Daffodil gives a runtime SDE on this. The assert test expression complains that "." has no value. I would claim this should either provide a value of 0 for this integer, or it should be a parse error because you must have at least 1 bit. Thoughts? Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | www.owlcyberdefense.com (Tresys is now part of Owl) Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy -- dfdl-wg mailing list dfdl-wg@ogf.org https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ogf.org_mailman_listinfo_dfdl-2Dwg&d=DwICAg&c=jf_iaSHvJObTbx-siA1ZOg&r=AJa9ThEymJXYnOqu84mJuw&m=mvRgmUZqqByvkZrWl9f4DONoCl3A8QR3HuliCUCmavs&s=AaalvDoqwfJgjWFrMa43i3Cqzxm_DXRA5jSZPaFoUY8&e= 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