0..n
Student
- sid:String- name:String
+ add()+ update()
1
User
- name:String- role:Long- realename:String
+ createCourse()
SignInList
- sid:String- title:String- limit:String
+ doSign()+ delete()
CourseItem
- name:String- type:String- courseId:String- order:int
+ download()+ remoce()
Group
- name:String- cout:int- items:Array- gId:int
+ expand()+ shrank()
Course
- title:String- cover:String- desc:String- courseId
+ add()+ update()+ end()
Reply
- title:String- count:String- publisher:String- cateateAt:String
+ count()+ delete()
Teacher
- tid:String- name:String
CourseItemResource
- name:String- type:String- cover:String- path:String- resourceId:String- courseItemId:String
+ play()+ delete()
Discusstion
- name:String- type:String- courseId:String- courseItemId:String
Class
- title:String- students:String- classId:String- courseId
