xml - How to force child element to have a value in XSD?

Question

I have XML (as an example) with a segment called Type within the segment Order. The segment is a one to many, so we have something like :

<Order>
  <Type>1</Type>
  <Type>2</Type>
  <Type>3</Type>
</Order>

Now the validation should be, that there always should be segment Type with value 1 in the segment Order, if not, a validation error should occur. I tried some validations, but could not get the correct result. Has someone thought on how to implement this and if this is even possible?

Answer 1

XSD 1.0

Your constraint cannot be expressed in XSD 1.0.

XSD 1.1

Your constraint can be expressed in XSD 1.1 using an assertion to state that there be at least one Type child of Order that has a value of 1:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
           vc:minVersion="1.1"> 
  <xs:element name="Order">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Type" maxOccurs="unbounded" type="xs:integer"/>
      </xs:sequence>
      <xs:assert test="Type = 1"/>
    </xs:complexType>
  </xs:element>
</xs:schema>