How to define restrictions between two elements in XSD

Question

Is it possible to define value restrictions between two elements in XML Schema?

Like in the following XSD:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
  targetNamespace="http://mydomain.com"
  xmlns="http://mydomain.com"
  elementFormDefault="qualified">

  <xs:element name="form">
    <xs:complexType>
      <xs:all>
        <xs:element name="metric1" type="xs:integer" />
        <xs:element name="metric2" type="xs:integer" />
      </xs:all>
    </xs:complexType>
  </xs:element>
</xs:schema>

Is there a way to define that the value of metric2 should greater than the value of metric 1? So that the following XML document would fail on validation:

<?xml version="1.0"?>
<form xmlns="http://www.ziya.gov.cn">
  <metric1>5</metric1>
  <metric2>3</metric2>
</form>

Answer 1

In XSD 1.1, define an assertion

<xs:assert test="metric2 gt metric1"/>

as part of the complexType definition.

XSD 1.1 is currently supported in Xerces, Saxon, and Altova.

If you're stuck with an XSD 1.0 processor then this constraint can't be defined.