"Database" structure in XML file

Question

So I have to define a "database" in an xml document that has to have a school, grades, rooms, courses and students and afterwards I have to write some classes in C# that has to get and save data to the xml file with the help of Deserialization and Serialization. But the problem is I don't know how I should structure the XML file, right now my file looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<School>
   <Grades>

   </Grades>
   <Rooms>

   </Rooms>
   <Courses>

   </Courses>
   <Students>

   </Students>
</School>

But I have been wondering if this might be a better way:

<?xml version="1.0" encoding="utf-8" ?>
<School>
   <Grades>
      <Rooms>
         <Courses>
            <Students>

            </Students>
         </Courses>
      </Rooms>
   </Grades>
</School>

Or maybe there is some third way I'm overlooking, any help would be appreciated

Answer 1

This question is opinion-based. So, this is just my opinion:

Choose the first layout and use attribute @IDs to link between them.
For example:

<?xml version="1.0" encoding="utf-8" ?>
<School>
   <Grades>
     <Grade id="gr1">...</Grade>
   </Grades>
   <Rooms>
     <Room id="rm1">...</Room>    
   </Rooms>
   <Courses>
     <Course id="crs1">
       <RoomNr>rm1</RoomNr>  <!-- Referring to the Rooms/Room/@id rm1 -->
       ...
     </Course>
   </Courses>
   <Students>
     <Student id="1">
       <Course>crs1</Course> <!-- Referring to the Courses/Course/@id crs1 -->
       <Course>...</Course>
     </Student>
   </Students>
</School>

This layout is easily query-able and changing the links won't significantly change the layout.

For example (Because you tagged your question with xslt):

• Retrieving all <Student>s can be done with the XPath-1.0 expression

  /School/Students/Student
  

• Retrieving all <Student>s which visit a certain course (e.g. crs1)

  /School/Students/Student[Course='crs1']
  

...and so on.