Você pode usar esse esquema XSD para validar o arquivo de relacionamento de usuários.
<?xml version="1.0"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="Relationships">
<xs:complexType>
<xs:sequence>
<xs:element name="Parent-Child" maxOccurs="unbounded" minOccurs="0">
<xs:complexType>
<xs:all>
<xs:element type="id" name="ChildId" minOccurs="1" maxOccurs="1" />
<xs:element type="id" name="ParentId" minOccurs="1" maxOccurs="1" />
</xs:all>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:simpleType name="id">
<xs:restriction base="xs:string">
<xs:maxLength value="50" />
</xs:restriction>
</xs:simpleType>
</xs:schema>