papers.xsd
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="acceptedworks">
<xs:complexType>
<xs:sequence>
<xs:element maxOccurs="10" minOccurs="2" ref="paper"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="paper">
<xs:complexType>
<xs:sequence>
<xs:element maxOccurs="unbounded" ref="author"/>
<xs:element ref="title"/>
<xs:element ref="abstract"/>
</xs:sequence>
<xs:attribute name="submitdate" use="required" type="st.date"/>
</xs:complexType>
</xs:element>
<xs:simpleType name="st.date">
<xs:restriction base="xs:string">
<xs:pattern value="\d{2}-\d{2}-\d{4}"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="author">
<xs:complexType>
<xs:attributeGroup ref="att.person"/>
</xs:complexType>
</xs:element>
<xs:attributeGroup name="att.person">
<xs:attribute name="firstname" use="required"/>
<xs:attribute name="lastname" use="required"/>
</xs:attributeGroup>
<xs:element name="title" type="xs:string"/>
<xs:element name="abstract" type="xs:string"/>
</xs:schema>

Event1.xml
<?xml version="1.0" encoding="UTF-8"?>
<acceptedworks xmlns:xsi="http://www.w3.org/2001/XMLSchemainstance"
xsi:noNamespaceSchemaLocation=" papers.xsd">
<paper submitdate="15-06-2010">
<author firstname="João" lastname="Silva"/>
<author firstname="José" lastname="Souza"/>
<title>Visão geral sobre XML</title>
<abstract>Este artigo trata dos conceitos de XML. O que
descrevemos aqui é tão verdade quanto 2+2=4. </abstract>
</paper>
<paper submitdate="01-06-2010">
<author firstname="Alfredo" lastname="Martins"/>
<author firstname="José" lastname="Souza"/>
<title>HTML4 x HTML5</title>
<abstract>Uma discução sobre as mudanças ocorridas com o
surgimento do HTML5 em comparação com o HTML4. </abstract>
</paper>
</acceptedworks>

Event2.xml
<?xml version="1.0" encoding="UTF-8"?>
<acceptedworks xmlns:xsi="http://www.w3.org/2001/XMLSchemainstance"
xsi:noNamespaceSchemaLocation=" papers.xsd">
<paper submitdate="02\12\2009">
<title>Matemática na infância.</title>
<abstract>Aplicabilidade de problemas para desenvolver o
raciocínio matemático em crianças menores de 5 anos.</abstract>
</paper>
<paper submitdate="10\04\2009">
<author firstname="Patrícia" lastname="Buarque"/>
<title>Pedras Pantaneiras</title>
<abstract>Levantamento dos tipos de pedras preciosas e semi
preciosas encontradas na planície pantaneira.</abstract>
</paper>
</acceptedworks>