Software Design

Include vs Extend in Library Circulation Systems

Use Case Diagrams · made in Skemio

UML use case diagram of a Library Circulation System showing Patron and Librarian actors with include and extend relationships for borrowing, returning, and fines.
UML use case diagram of a Library Circulation System showing Patron and Librarian actors with include and extend relationships for borrowing, returning, and fines.
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What it shows

  • Include links mark unconditional sub-tasks like updating catalog RFID tags.
  • Extend links capture optional or exceptional flows like fine collection.
  • Borrower and staff actor boundaries keep privilege models unambiguous.

The takeaway

Include is mandatory execution; extend is optional or conditional execution.

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