An XSD for validating the updated mapping.xml file (i.e. including validation-rules)

mapping-validator-updates.xsd

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="xml.xsd"/>

<xsd:element name="mappings">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element ref="mapping" minOccurs="1" maxOccurs="unbounded" />
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

<xsd:element name="mapping">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element name="path" type="xsd:string" minOccurs="1" maxOccurs="1" />
      <xsd:element name="codelist" minOccurs="1" maxOccurs="1">
        <xsd:complexType>
          <xsd:attribute name="ref" type="xsd:string" use="required" />
        </xsd:complexType>
      </xsd:element>
      <xsd:element name="condition" type="xsd:string" minOccurs="0" maxOccurs="1" />
      <xsd:element ref="validation-rules" minOccurs="1" maxOccurs="1" />
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

<xsd:element name="validation-rules">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element ref="validation-rule" minOccurs="1" maxOccurs="unbounded" />
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

<xsd:element name="validation-rule">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element name="priority" type="xsd:string" minOccurs="1" maxOccurs="1" />
      <xsd:element name="severity" type="xsd:string" minOccurs="1" maxOccurs="1" />
      <xsd:element name="category" type="xsd:string" minOccurs="1" maxOccurs="1" />
      <xsd:element name="id" type="xsd:string" minOccurs="1" maxOccurs="1" />
      <xsd:element name="message" type="xsd:string" minOccurs="1" maxOccurs="1" />
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

</xsd:schema>