sample.xsd
 
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'>

 <xs:complexType name="eventDefinitionsType">
                <xs:sequence>
                        <xs:element name="event-def" type="ems:eventDefType" minOccurs="0" maxOccurs="unbounded"/>
                </xs:sequence>
        </xs:complexType>

<xs:complexType name="eventDefType">
                <xs:attribute name="name" type="eventDefNameType" use="required"/>
                <xs:attribute name="version" type="eventDefVersionType" use="optional" default="1"/>
                <xs:attribute name="severity" type="eventDefSeverityType" use="required"/>
        </xs:complexType>

<xs:attribute name="name" type="eventDefNameType" use="required"/>
 <xs:attribute name="severity" type="SeverityType" use="required"/>
 <xs:attribute name="version" type="VersionType" use="optional" default="1"/>