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On Thu, Sep 27, 2018 at 6:24 PM Costello, Roger L. <costello@mitre.org> wrote:

Here is an element with simple content and an attribute:

<Cost currency="USD">8.95</Cost>


The data USD is explicitly labeled. The label indicates that USD is a currency.

What about the data 8.95, is it labeled? No! It is anonymous/unlabeled. Note: Cost is not the label for 8.95; Cost is the label for the whole package.

In my most recent post, I asked, “What is that number (8.95)?” I received excellent responses: 8.95 is a price, 8.95 is an amount, etc. External knowledge was needed to label the data. The need for external knowledge completely contradicts the fundamental axiom of XML.

Therefore, don’t create XML like this:

<Cost currency="USD">8.95</Cost>

instead, create XML like this:


If you can use a schema, to validate an XML document, I think an XML like <Cost currency="USD">8.95</Cost> can be considered sufficiently labelled (8.95 as well). Following is my 1st attempt to create such a schema document for <Cost currency="USD">8.95</Cost>,

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="Cost">
          <xs:extension base="Amount">
             <xs:attribute name="currency" type="Currency" use="required"/>
  <xs:simpleType name="Amount">
     <xs:restriction base="xs:decimal">
        <xs:minInclusive value="0"/>
  <xs:simpleType name="Currency">
     <xs:restriction base="xs:string">
        <xs:enumeration value="USD"/>
        <xs:enumeration value="GBP"/>


Mukul Gandhi

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