Embedded validation within XSD schema

Question

I would like to have rules embedded within my XSD schema definition for how optional attributes of an element are to be used. Consider the following element definition:

<xs:complexType name="sampleElement">
  <xs:attribute name="name" type="xs:string" use="required"/>
  <xs:attribute name="description" type="xs:string" use="optional"/>
  <xs:attribute name="optPrimary" type="xs:string" use="optional"/>
  <xs:attribute name="optSecondary" type="xs:string" use="optional"/>
</xs:complexType

In this example, both optPrimary and optSecondary are indeed optional. The attribute optPrimary can be used by itself, but optSecondary must be used in conjunction with optPrimary. Therefore, I would like a rule embedded in the schema that can be enforced when the XML is validated.

I have found examples of Schematron used for this in a separate file, but I have not found how it can be embedded as part of the schema.

XML schema does not support the ability to create constraints between elements. You have correctly identified schematron which addresses this gap. — Mark O'Connor

Petru Gardea Petru Gardea · Accepted Answer · 2014-02-07T02:29:28

XSD 1.1 supports this. This is one way of expressing it:

<?xml version="1.0" encoding="utf-8" ?>
<!-- XML Schema generated by QTAssistant/XSD Module (http://www.paschidev.com) -->
<xsd:schema targetNamespace="http://tempuri.org/XMLSchema.xsd" xmlns="http://tempuri.org/XMLSchema.xsd" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xerces="http://xerces.apache.org">
    <xsd:element name="sampleElement">
        <xsd:complexType>
            <xsd:attribute name="name" type="xsd:string" use="required"/>
            <xsd:attribute name="description" type="xsd:string" use="optional"/>
            <xsd:attribute name="optPrimary" type="xsd:string" use="optional"/>
            <xsd:attribute name="optSecondary" type="xsd:string" use="optional"/>
            <xsd:assert test="@optPrimary or not(@optSecondary)" xerces:message="Secondary needs primary..."/>
        </xsd:complexType>          
    </xsd:element>
</xsd:schema>

Embedded validation within XSD schema

1 Answers