我正在为这里给出的 XML 编写 DTD。 http://s3.amazonaws.com/spark-public/db/docs/courses-ID.xml
我不知道如何编写部门元素。这是我的 DTD 代码。
<!ELEMENT Course_Catalog (Department+)>
<!ELEMENT Department ---**don't know what to write here**--->
<!ATTLIST Department Code CDATA #REQUIRED Chair IDREF #REQUIRED>
<!ELEMENT Title (#PCDATA)>
<!ELEMENT Course (Title,Description*)>
<!ELEMENT Professor (First_Name,Middle_Initial?,Last_Name)>
<!ELEMENT Lecturer (First_Name,Middle_Initial?,Last_Name)>
<!ATTLIST Course Number ID #REQUIRED Prerequisites IDREFS #IMPLIED Instructors IDREFS #REQUIRED Enrollment CDATA #IMPLIED>
<!ATTLIST Professor InstrID ID #REQUIRED>
<!ATTLIST Lecturer InstrID ID #REQUIRED>
<!ELEMENT First_Name (#PCDATA)>
<!ELEMENT Middle_Initial (#PCDATA)>
<!ELEMENT Last_Name (#PCDATA)>
<!ELEMENT Description (#PCDATA | Courseref)*>
<!ELEMENT Courseref EMPTY>
<!ATTLIST Courseref Number IDREF #REQUIRED>
请帮我。