As I said in my comment this is only valid if first
and second
are elements (not attributes). The |
xpath operator it's like a union of nodes.
<xs:element name="exampleElement" type="exampleType">
<xs:unique name="firstAndSecondDifferent">
<xs:selector xpath="first | second" />
<xs:field xpath="." />
</xs:unique>
</xs:element>
<xs:complexType name="exampleType">
<xs:sequence>
<xs:element name="first" type="xs:integer" />
<xs:element name="second" type="xs:integer" minOccurs="0" />
</xs:sequence>
</xs:complexType>
The following element is valid (first
and second
have different values):
<exampleElement>
<first>1</first>
<second>5</second>
</exampleElement>
The following element is valid (no second
element present):
<exampleElement>
<first>1</first>
</exampleElement>
The following element is not valid (first
and second
have the same value):
<exampleElement>
<first>1</first>
<second>1</second>
</exampleElement>
This can't be done with attributes because selector xpath
doesn't allow to use attributes so "@first | @second"
it's not a valid value of the xpath attribute of a selector.