简单的XML问题

好了，用我的XML编辑器来检查我得到“验证停在第2行，第8列验证：？没有声明发现元素‘员工’有谁知道这是为什么简单的XML问题

另外，每三名员工都是不同的类型，每种类型都包含不同的元素（辅助员工成员只有电子邮件，姓名，职位等，而FullTime类型具有所有元素的信息）。数据留空了吗？如果他们是不同类型的职员，可以摆脱多余的元素还是每个员工都需要相同的元素？谢谢！

<Staff> 

    <StaffMember type="FullTime"> 
     <Name>Richard Baskerville</Name> 
     <Position>Professor</Position> 
     <OfficePhone>(404) 413-7362</OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>919</Room> 
     <URL>www.cis.gsu.edu/~rbaskerv</URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo>Ph. D., M.S., B.S.</DegreeInfo> 
     <Research> Information systems security, interaction of information systems and organizations, qualitative research methods,  diffusion of IT innovations, knowledge management</Research> 
    </StaffMember> 

    <StaffMember type ="FullTime"> 
     <Name>Michael Gallivan</Name> 
     <Position>Associate Professor</Position> 
     <OfficePhone>(404) 413-7363</OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>935</Room> 
     <URL>www.cis.gsu.edu/~mgalliva</URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo>Ph. D., M.B.A., M.P.H., B.A.</DegreeInfo> 
     <Research> IT human resource management, management of IT outsourcing, adoption and diffusion of innovations, organizational learning from innovations </Research> 
    </StaffMember> 

     <StaffMember type ="FullTime"> 
     <Name>Sidney Harris</Name> 
     <Position>Professor</Position> 
     <OfficePhone>(404) 413-7017</OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>427</Room> 
     <URL>www2.gsu.edu/~wwwseh/</URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo>Ph. D., M.S., B.S.</DegreeInfo> 
     <Research> Strategic management of technology, global practices in technological innovation and management, regional studies on China and Asia culture of high performance organization</Research> 
    </StaffMember> 

     <StaffMember type ="Adjunct"> 
     <Name>Arash Akhlaghi</Name> 
     <Position>Adjunct Professor</Position> 
     <OfficePhone></OfficePhone> 
     <Building></Building> 
     <Room></Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Adjunct"> 
     <Name>Catherine Baird</Name> 
     <Position>Adjunct Professor</Position> 
     <OfficePhone></OfficePhone> 
     <Building></Building> 
     <Room></Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Adjunct"> 
     <Name>David Bloomquist</Name> 
     <Position>Adjunct Professor</Position> 
     <OfficePhone></OfficePhone> 
     <Building></Building> 
     <Room></Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Staff"> 
     <Name>Desiree Plummer</Name> 
     <Position>PC System Specialist</Position> 
     <OfficePhone>(404) 413-7440></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>908</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Staff"> 
     <Name>Walter Rich</Name> 
     <Position>Manager, CIS External Affairs</Position> 
     <OfficePhone>(404) 413-7398></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>929</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Staff"> 
     <Name>James Sneed</Name> 
     <Position>Information Technology Department Manager</Position> 
     <OfficePhone>(404) 413-7383></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>907</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Ph.D"> 
     <Name>Anouck Adrot</Name> 
     <Position></Position> 
     <OfficePhone>(404) 413-7389></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>910</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Ph.D"> 
     <Name>Chad Anderson</Name> 
     <Position></Position> 
     <OfficePhone>(404) 413-7389></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>910</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

    <StaffMember type="Ph.D"> 
     <Name>Mathieu Chauvet</Name> 
     <Position></Position> 
     <OfficePhone>(404) 413-7389></OfficePhone> 
     <Building>Robinson College</Building> 
     <Room>910</Room> 
     <URL></URL> 
     <Email>[email protected]</Email> 
     <DegreeInfo></DegreeInfo> 
     <Research></Research> 
    </StaffMember> 

</Staff>