xml schema check that restriction enumeration value only occrus once

I am creating a xsd schema开发者_运维知识库 for validation of some xml

I would like to restrict the xml so it's not posible to input the same item twice:

<branches>
   <branche>Bank</branche>
   <branche>Bank</branche>
</branches>

But it must be posible to use 2 different items:

<branches>
   <branche>Bank</branche>
   <branche>Insurance</branche>
</branches>

So i have the following code:

<!-- definition of simple elements -->
    <xs:simpleType name="branche">
        <xs:restriction base="xs:string">
            <xs:enumeration value="Bank" maxOccurs="1"/>
            <xs:enumeration value="Insurance" maxOccurs="1"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:element name="branches" minOccurs="0"> <!-- minOccurs becouse i want it to be posible to leave out the whole <branches> tag -->
        <xs:complexType>
            <xs:sequence>
                <xs:element name="branche" type="branche" minOccurs="0" maxOccurs="2" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

using the maxOccurs="1" does not restrict it to only one value because the 'branche' tag can occur twice.

I want the value (<branche>value</branche>) to be unique.

thnx!

See examples on identity constraints here. Something like:

<xs:element name="branches" ...>
  <xs:unique name="...">
    <xs:selector xpath="branche"/>
    <xs:field xpath="."/>
  </xs:key>
</xs:element>

Not quite sure about the syntax, but you get the idea.

Fixed it by using the following code:

<xs:element name="branches" minOccurs="0">
   <xs:complexType>
      <xs:sequence>
         <xs:element name="branche" type="branche" minOccurs="0" maxOccurs="2" />
      </xs:sequence>
   </xs:complexType>
   <xs:unique name="brancheUnique">
      <xs:selector xpath="branche"/>
      <xs:field xpath="."/>
   </xs:unique>
</xs:element>

thnx lexicore for pointing me in the right direction