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?
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