=?UTF-8?Q?Re=3A_=5Bxml=2Ddev=5D_Don=E2=80=99t_create_elements_with_simpl

[Mukul Gandhi <gandhi.mukul@gmail.com>]

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:

<Cost>
    <Currency>USD</Currency>
    <Amount>8.95</Amount>
</Cost>

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:complexType>

       <xs:simpleContent>

          <xs:extension base="Amount">

             <xs:attribute name="currency" type="Currency" use="required"/>

          </xs:extension>

       </xs:simpleContent>

     </xs:complexType>

  </xs:element>

  

  <xs:simpleType name="Amount">

     <xs:restriction base="xs:decimal">

        <xs:minInclusive value="0"/>

     </xs:restriction>

  </xs:simpleType>

  

  <xs:simpleType name="Currency">

     <xs:restriction base="xs:string">

        <xs:enumeration value="USD"/>

        <xs:enumeration value="GBP"/>

     </xs:restriction>

  </xs:simpleType>

</xs:schema>

--

Regards,

Mukul Gandhi