Xpath in xml file

Hello i try to make a XPath queries but i cant take a result . the query is Record/Teacher[TeacherID=parent::Record/Conservatory[ConservatoryID='C100']/Name]

The xml file is

<?xml version="1.0" encoding="UTF-8" ?>

<Record xsi:noNamespaceSchemaLocation="C:\Users\vagos\Desktop\db.xsd" xmlns:xs="http://ift.tt/tphNwY" xmlns:xsi="http://ift.tt/ra1lAU">

    <Conservatory ConservatoryID="C100">
        <Name>...</Name>
        <Address>
            <Street>..</Street>
            <Zip>...</Zip>
            <City>...</City>
        </Address>
    </Conservatory>


    <Student StudentID="S100">
        <ConservatoryID fkConservatoryID="C100"/>
        <Name>...</Name>
        <Address>
            <Street>.....</Street>
            <Zip>....</Zip>
            <City>.....</City>
        </Address>
    </Student>

    <Teacher TeacherID="T100">
        <ConservatoryID fkConservatoryID="C100"/>
        <Name>......</Name>
        <Name_speciality>....</Name_speciality>
    </Teacher>

    <Instrument InstrumentID="I100">
        <ConservatoryID fkConservatoryID="C100"/>
        <TeacherID fkTeacherID="T100"/>
        <StudentID fkStudentID="100"/>
        <Name>.....</Name>
        <InstrumentType>.....</InstrumentType>  
    </Instrument>


</Record>

The xsd file

<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSpy v2009 (http://www.altova.com) by Aruna (Nil) -->
<xs:schema xmlns:xs="http://ift.tt/tphNwY" elementFormDefault="qualified" attributeFormDefault="unqualified">
                <xs:element name="Record" maxOccurs="unbounded">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="Conservatory" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="Name" type="xs:string"/>
                                        <xs:element name="Address" type="AddressType"/>
                                    </xs:sequence>
                                    <xs:attribute name="ConservatoryID" type="xs:string" use="required"/>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="Student" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xsd:complexType>
                                          <xsd:attribute name="fkConservatoryID" type="xsd:string" use="required"/>
                                       </xsd:complexType>
                                        <xs:element name="Name" type="xs:string"/>
                                        <xs:element name="Address" type="AddressType"/>
                                    </xs:sequence>
                                    <xs:attribute ref="StudentID" type="xs:string" use="required"/>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="Teacher" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xsd:complexType>
                                          <xsd:attribute name="fkConservatoryID" type="xsd:string" use="required"/>
                                        </xsd:complexType>
                                        <xs:element name="Name" type="xs:string"/>
                                        <xs:element name="Name_speciality" type="xs:string"/>
                                    </xs:sequence>
                                    <xs:attribute ref="TeacherID" type="xs:string" use="required"/>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="Instrument" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xsd:complexType>
                                          <xsd:attribute name="fkConservatoryID" type="xsd:string" use="required"/>
                                          <xsd:attribute name="fkTeacherID" type="xsd:string" use="required"/>
                                          <xsd:attribute name="fkStudentID" type="xsd:string" use="required"/>
                                        </xsd:complexType>
                                        <xs:element name="Name" type="xs:string"/>
                                        <xs:element name="InstrumentType" type="xs:string"/>
                                    </xs:sequence>
                                    <xs:attribute ref="InstrumentID" type="xs:string" use="required"/>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="AddressType" maxOccurs="unbounded">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="Street" type="xs:string"/>
                                        <xs:element name="Zip" type="xs:string"/>
                                        <xs:element name="City" type="xs:string"/>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                    </xs:complexType>
                    <xs:key name="PKConservatory">
                        <xs:selector xpath="Conservatory"/>
                        <xs:field xpath="@ConservatoryID"/>
                    </xs:key>
                    <xs:key name="PKStudent">
                        <xs:selector xpath="Student"/>
                        <xs:field xpath="@StudentID"/>
                    </xs:key>
                    <xs:key name="PKTeacher">
                        <xs:selector xpath="Teacher"/>
                        <xs:field xpath="@TeacherID"/>
                    </xs:key>
                    <xs:key name="PKInstrument">
                        <xs:selector xpath="Instrument"/>
                        <xs:field xpath="@InstrumentID"/>
                    </xs:key>
                    <xs:keyref name="FKStudentToConservatory" refer="PKConservatory">
                        <xs:selector xpath="Student"/>
                        <xs:field xpath="@fkConservatoryID"/>
                    </xs:keyref>
                    <xs:keyref name="FKTeacherToConservatory" refer="PKConservatory">
                        <xs:selector xpath="Teacher"/>
                        <xs:field xpath="@fkConservatoryID"/>
                    </xs:keyref>
                    <xs:keyref name="FKInstrumentToConservatory" refer="PKConservatory">
                        <xs:selector xpath="Instrument"/>
                        <xs:field xpath="@fkConservatoryID"/>
                    </xs:keyref>
                    <xs:keyref name="FKInstrumentToTeacher" refer="PKTeacher">
                        <xs:selector xpath="Instrument"/>
                        <xs:field xpath="@fkTeacherID"/>
                    </xs:keyref>
                    <xs:keyref name="FKInstrumentToStudent" refer="PKStudent">
                        <xs:selector xpath="Instrument"/>
                        <xs:field xpath="@fkStudentID"/>
                    </xs:keyref>
                 </xs:element>
</xs:schema>