There is no built-in XSD type that corresponds to the ASN.1 BIT STRING type. For this reason, a custom type was created in the ASN2XSD run-time library (asn1.xsd) to model this type. This type is asn1:BitString and has the following definition:

   <xsd:simpleType name="BitString">
      <xsd:restriction base="xsd:token">
         <xsd:pattern value="[0-1]{0,}"/>
      </xsd:restriction>
   </xsd:simpleType>

The ASN.1 BIT STRING type is converted into a reference to this custom type as follows:

ASN.1 production:

   TypeName ::= BIT STRING

Generated XSD code:

   <xsd:simpleType name="TypeName">
      <xsd:restriction base="asn1:BitString"/>
   </xsd:simpleType>