Understanding code list declarations

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

Hi folks!

I'm working on my code list obligations and I'm confused about 
something that I see in the UBL 2 schemas.

I note the following in my analysis:

   <Context item="@cbc:amountCurrencyID" codes="CurrencyCodeContentType"/>
   <Context item="cac:CurrencyCode" codes="CurrencyCodeType"/>
   <Context item="in:InvoiceCurrencyCode" codes="CurrencyCodeType"/>
   <Context item="in:PricingCurrencyCode" codes="CurrencyCodeType"/>
   <Context item="cac:SourceCurrencyCode" codes="CurrencyCodeType"/>
   <Context item="cac:TargetCurrencyCode" codes="CurrencyCodeType"/>
   <Context item="in:TaxCurrencyCode" codes="CurrencyCodeType"/>

What caught my eye was the existence of both 
"CurrencyCodeContentType" (which is constrained to the ISO list) and 
"CurrencyCodeType" (which is unconstrained):

   <xsd:simpleType name="CurrencyCodeContentType">
     <xsd:restriction base="xsd:token">
       <xsd:enumeration value="AED">
         <xsd:annotation ...

   <xsd:complexType name="CurrencyCodeType">
     ...
     <xsd:simpleContent>
       <xsd:extension base="xsd:normalizedString">
         <xsd:attribute ...

I'm curious why we don't constrain all currency values the same way 
... is this an oversight in the schemas?

If not, which of the following should I provide to trading partners 
needing code list value validation?

   - only one degree of flexibility (all currencies),
   - two degrees of flexibility (CurrencyCodeContentType and CurrencyCodeType)
   - seven degrees of flexibility (@cbc:amountCurrencyID, 
cac:CurrencyCode, in:InvoiceCurrencyCode, in:PricingCurrencyCode, 
cac:SourceCurrencyCode, cac:TargetCurrencyCode, and in:TaxCurrencyCode)?

Thanks for your guidance!

. . . . . . . . . . . . Ken

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