[DFDL-WG] What is Rationale why Nillable complex type elements can only have '%ES; ' as their dfdl:nilValue property

[Steve Hanson]

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 at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday 



From:   "Mike Beckerle" <mbeckerle.dfdl at gmail.com>
To:     "DFDL-WG" <dfdl-wg at 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 at 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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