XSD: how to restrict number of characters in string type attribute?

You need to create a simple type like so:

  <xs:simpleType name="LimitedString">
    <xs:restriction base="xs:string">
      <xs:maxLength value="50" />
    </xs:restriction>
  </xs:simpleType>

and then use this new type in your schema:

  <xs:complexType name="test">
    <xs:sequence>
      <xs:element name="abc" type="xs:String" />
    </xs:sequence>
    <xs:attribute type="LimitedString" name="myattr" />
  </xs:complexType>

Marc

You can restrict the string to a number of chars like this:

<xs:simpleType name="threeCharString">
  <xs:annotation>
    <xs:documentation>3-char strings only</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:string">
    <xs:length value="3"/>
  </xs:restriction>
</xs:simpleType>

The xs:length in the above limits the length of the string to exactly 3 chars. You can also use xs:minLength and xs:maxlength, or both.

You can provide a pattern like so:

<xs:simpleType name="fourCharAlphaString">
  <xs:restriction base="xs:string">
    <xs:pattern value="[a-zA-Z]{4}"/>
  </xs:restriction>
</xs:simpleType>

The above says, 4 chars, of any of a-z, A-Z. The xs:pattern is a regular expression, so go to town with it.

You can restrict the string to a particular set of strings in this way:

<xs:simpleType name="iso3currency">
  <xs:annotation>
    <xs:documentation>ISO-4217 3-letter currency codes. Only a subset are defined here.</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:string">
    <xs:length value="3"/>
    <xs:enumeration value="AUD"/>
    <xs:enumeration value="BRL"/>
    <xs:enumeration value="CAD"/>
    <xs:enumeration value="CNY"/>
    <xs:enumeration value="EUR"/>
    <xs:enumeration value="GBP"/>
    <xs:enumeration value="INR"/>
    <xs:enumeration value="JPY"/>
    <xs:enumeration value="RUR"/>
    <xs:enumeration value="USD"/>
  </xs:restriction>
</xs:simpleType>

The answer by marc_s would require you to define a new type for every possible string length you might use. Instead you can define the restriction directly on the attribute itself.

  <xs:complexType name="Test">
    <xs:attribute name="LimitedString">
      <xs:simpleType>
        <xs:restriction base="xs:string">
          <xs:maxLength value = "50"/>
        </xs:restriction>
      </xs:simpleType>
    </xs:attribute>
  </xs:complexType>