See spec section 13.15. "to avoid the concept of a complex element having a value, which does not exist in DFDL". The parser would not know to treat the '-' as the nil value for the complex element, or the content of the first child? Allowing just %ES; avoids that. 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: 01/12/2021 21:07 Subject: [EXTERNAL] [DFDL-WG] What is Rationale why Nillable complex type elements can only have '%ES; ' as their dfdl:nilValue property Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org> DFDL has this seemingly ad-hoc restriction. Users naturally want to model a complex element where "-" (dash) means the whole complex element is nilled, and if not "-" then we parse and produce a complex element. What is the rationale for this restriction? -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg 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