Aggregate components: XML complexType and type= vs. ref=

["Michael Strasser" <Michael.Strasser@brisbane.qld.gov.au>]

I am learning about (and hopefully contributing to) the Australian
standard called eDAIS: electronic Development Assessment
Interoperability Specification.

eDAIS is defined in UML using a methodology derived from UN/CEFACT
Modelling Methodology (UMM).

The XML schemas exported from the model define all aggregate components
using constructs like:

  <xs:element name="Application" type="da:Application"/>

which surprises me because of the ‘wrong namespace’ documents that
result:

  <pcat:ProposeCreateApplicationTransaction>
    <!-- Application element is defined in da namespace. -->
    <pcat:Application>
      <da:ApplicationNumber>123456</da:ApplicationNumber>
      <!-- etc. -->
    </pcat:Application>
  </pcat:ProposeCreateApplicationTransaction>

The creators of eDAIS inform me that they are following the UN/CEFACT
XML Naming and Design Rules 2.0. On my first reading of that document it
appears to specify this schema design but isn’t very clear.

But I notice that UBL, which has similar provenance, uses references
like this:

  <xs:element ref="cac:OrderLine" maxOccurs="unbounded"/>

I think the use of references is better because it creates XML
documents that are more easily processed: all components are in their
‘correct’ namespaces.

Can someone please explain the decision-making process for UBL and how
it was decided to apparently contradict the UN/CEFACT rules? Or are the
‘rules’ not so clear-cut? I have read the UBL 2.0 NDR and I am even
more confused (i.e. doesn’t [RED2] contradict [ELD3]?)!


Thanks in advance

Michael Strasser
Brisbane, Australia

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