##steps

• visualize and find entities
• establish association
  • IS-A - generalization (parent - child)
  • association
    • aggragation (child can survive if a parent destroy)
    • composition(child destroyed survive if a parent destroy)
• establish cardinality
  • one to one
  • one to many
  • many to one
  • many to many
    • #####trick to find cardinality
    • for two object A, and B
      • ask object A, for 1 instance how many object B occur?
      • ask object B, for 1 instance how many object A occur?
    • example : student - book
      • 1 student borrow one book
      • 1 book borrowed by many students (Many to one )
• indentify functionalities
• API design
• Implementation
• Testing

• Author
• Book
• Student
• Transaction

• Book
  • create book (author part of book, create author if not exists)
  • find by ID, author, genere
  • find all
• Student
  • create student
  • find student by Id
  • find all students
• Transaction
  • create issue book transaction with bookId and studentId
  • create return book transaction with bookId and studentId