[DFDL-WG] Proposal: Adopt experimental emptyElementParsePolicy property in DFDL v1.0

[Mike Beckerle]

A feature is described in https://redmine.ogf.org/dmsf_files/13596?download=
.

It describes a new property to control parser behavior which is already
implemented as the standard behavior by IBM DFDL and as an optional
experimental behavior by Daffodil. This is desirable functionality and it
is needed for some interoperability between these implementations; hence, I
propose it be included in the DFDL 1.0 spec., however, aspects that aren't
implemented by all implementations of DFDL should be made optional features.

We would have to create an erratum for it. I suggest the following are the
changes that would be needed.

* Section 9.4.2 is amended by inserting a new first paragraph

"The property dfdl:emptyElementParsePolicy controls the behavior when empty
representation is established while parsing. If
dfdl:emptyElementParsePolicy is 'treatAsAbsent', then the empty
representation is treated the same as the absent representation, and no
default values are considered for addition to the infoset. The remainder of
this section describes the behavior for
dfdl:emptyElementParsePolicy='treatAsEmpty'."

* Section 12.2 - Property description from experimental features document
goes right after dfdl:emptyElementDelimiterPolicy.

* Section 21 - The row for feature "Defaults" is modified. In the Detection
column add  "dfdl:emptyElementParsePolicy='treatAsEmpty'".

The upshot of this change is that we have the pain in the neck of
introducing a new property to implementations, but what we get is that IBM
DFDL behavior and Daffodil behavior are then both conforming to the DFDL
spec. This
is way better than having to document non-conformance or deal with
extension features (that not everyone has) to obtain portability.

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
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