How do I create a reusable "US State" type in an XML schema?

Question

I have an XML schema that includes multiple addresses:

<xs:element name="personal_address" maxOccurs="1">
  <!-- address fields go here -->
</xs:element>
<xs:element name="business_address" maxOccurs="1">
  <!-- address fields go here -->
</xs:element>

Within each address element, I include a "US State" enumeration:

<xs:simpleType name="state">
    <xs:restriction base="xs:string">
     <xs:enumeration value="AL" />
     <xs:enumeration value="AK" />
     <xs:enumeration value="AS" />
                ....
            <xs:enumeration value="WY" />
        </xs:restriction>
</xs:simpleType>

How do I go about writing the "US State" enumeration once and re-using it in each of my address elements? I apologize in advance if this is a n00b question -- I've never written an XSD before.

My initial stab at it is the following:

<xs:element name="business_address" maxOccurs="1">
  <!-- address fields go here -->
  <xs:element name="business_address_state" type="state" maxOccurs="1"></xs:element>
</xs:element>

Answer 1

I think you are on the right tracks. I think its more to do with XML namespaces. Try the following:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.example.org/foo"
    xmlns:tns="http://www.example.org/foo"
    elementFormDefault="qualified">
    <xs:element name="business_address">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="business_address_state"
                    type="tns:state" maxOccurs="1" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:simpleType name="state">
        <xs:restriction base="xs:string">
            <xs:enumeration value="AL" />
            <xs:enumeration value="AK" />
            <xs:enumeration value="AS" />
            <xs:enumeration value="WY" />
        </xs:restriction>
    </xs:simpleType>
</xs:schema>

Note that the type is tns:state not just state

And then this is how you would use it:

<?xml version="1.0" encoding="UTF-8"?>
<business_address xmlns="http://www.example.org/foo"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.example.org/foo foo.xsd ">
    <business_address_state>AL</business_address_state>
</business_address>

Notice that this XML uses a default namespace the same as the targetNamespace of the XSD