1<?xml version="1.0"?>
2<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
3   <xsd:element name= "contact" type="ContactType"/>
4   <xsd:complexType name="ContactType">
5      <xsd:choice minOccurs="1" maxOccurs="2">
6         <xsd:element name="customer" type="xsd:string" />
7         <xsd:element name="comment" type="xsd:string"  minOccurs="0"/>
8      </xsd:choice>
9   </xsd:complexType>
10</xsd:schema>
11