This is definitely a DFDL language restriction, not a Daffodil-specific
thing.
I have made inquiries as to what the rationale is for this restriction, and
I'll report back.
In the mean time, maybe this sort of technique.
<choice>
<element name="noValue" type="xs:string" dfdl:lengthKind="explicit"
dfdl:length="0" dfdl:initiator="-"/>
<element name="myComplexType">
.... non nillable complex type definition ....
</element>
</choice>
I have to admit that this workaround sort of suggests that there isn't a
coherent rationale for the restriction, as this is pretty obviously
equivalent to the complex type being nillable with nilValue="-".
On Wed, Dec 1, 2021 at 12:43 PM Roger L Costello <coste...@mitre.org> wrote:
> Hi Folks,
>
> I am creating a DFDL schema for a data format that has a field whose value
> is a hyphen when no data is available and when data is available, then the
> field contains either an ISO datetime or a 3-letter month name. Here's how
> I specified the field:
>
> <xs:element name="MyField" nillable="true" dfdl:nilValue="-">
> <xs:complexType>
> <xs:choice dfdl:choiceLengthKind="implicit">
> <xs:element name="DateTimeIso">
> <xs:complexType>
> <xs:sequence>
> ...
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="MonthName" type="xs:string"
> dfdl:length="3" dfdl:lengthKind="explicit" />
> </xs:choice>
> </xs:complexType>
> </xs:element>
>
> When I run it, Daffodil gives this error message:
>
> [error] Schema Definition Error: Nillable complex type elements can only
> have '%ES;' as their dfdl:nilValue property.
>
> Is that an error in Daffodil? Or, is it an actual DFDL restriction? If the
> latter, why is there such a restriction? How do I work around this error?
>
> /Roger
>
