Improvement of Group E-r Chart

It's my improvement to our team's database E-r diagram.

I added a student message to the attendance, because our group explained in the requirement analysis that there is a teacher and student through this software communication function, teachers can use this function to leave a message to students, students can also use this function to leave or explain the reasons for absenteeism. There is another improvement is that I think the time table with the teacher's relationship has a problem, before we are a classroom teacher corresponding to a time table, but if the teacher is sick or leave, the substitute teachers can continue to record work through the same attendance table.

These are my improvements to our group, and eventually I will finalize the final version with the team members.

Improvement of Group E-r Chart