How do I enforce a schema with an element that has a specific attribue value?

Question

My XML document looks like:

<Entries>
  <entry key="some string" value="some string"/>
  " "
  " "
  " "
</Entreis>

I need to enforce a rule that one of the entry elements must have a key of value "Version". What would the schema look like?

I tried

<xs:element name ="Entries">
  <xs:complexType>
    <xs:sequence minOccurs="1" maxOccurs="1">
      <xs:element name="entry">
        <xs:attribute name="key" fixed="Version" type="xs:string/>
        <xs:attribute name="value" type="xs:string/>
      </xs:element>
    </xs:sequence>
    <xs:sequence minOccurs="0" maxOccurs="unbounded">
      <xs:element name="entry">
        <xs:attribute name="key" type="xs:string/>
        <xs:attribute name="value" type="xs:string/>
      </xs:element>
    </xs:sequence>
  </xs:complexType>
 </xs:element>

but I get a validation error saying that I cannot have sequence appear twice in a complex type or that it is invalid or misplaced.

Answer 1

I'm afraid it cannot be done in xsd 1.0. You cannot have two elements with the same name but different (although similiar) structure at one place.

On the other side - what should @key="Version" express? Couldn't be this information presented as a part of Entries element (somthing like <Entries version="..">)?