NOTE: I am self studying UML so I have nobody to verify my diagrams and hence I am posting here, so please bear with me. This is the problem I got from some PDF available on Google that simply had the following problem statement: Problem Statement:A library contains books and journals. The task is to develop a computer system for borrowing books. In order to borrow a book the borrower must be a member of the library. There is a limit on the number of books that can be borrowed by each member of the library. The library may have several copies of a given book. It is possible to reserve a book. Some books are for short term loans only. Other books may be borrowed for 3 weeks. Users can extend the loans.Draw a use case diagram for a library.I already drew the Use Case diagram and had it checked by a community member. This time I drew  sequence diagrams for borrowing a book and extending the date of return.Please let me know if they are correct.I drew them using Visual Paradigm and I dont know how to keep a control of the sequence numbers. If you do, please let me know :)Diagrams
Is my sequence diagram correct?
uml;modeling;sequence diagram
They seem to be correct enough to understand what is going on, which in my opinion is all you need for UML. However if you want to be more technically correct:Request membership card appears to be a return when it should presumably be a message with provide membership card as a return? confirm membership may not need to go back to the person, but a request for the book name probably should