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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 Borrowing

Extending the date

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This might be a better fit for CodeReview.SE. –  Walter Sep 5 '12 at 14:29
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up vote 2 down vote accepted

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
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Oh I forgot to return the membership card! :p and yes, I agree with your first point. It should not be a return message –  Dummy Derp Sep 5 '12 at 15:00
just a question with regards to DFD: is it necessary to show inputs on left and outputs on right? –  Dummy Derp Sep 5 '12 at 15:49
necessary, no, if its possible then it can make the diagram easier to understand –  jk. Sep 5 '12 at 16:11
OK, thanks for letting me know :) –  Dummy Derp Sep 5 '12 at 16:54
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