The scenario
A library system needs to model books, copies, members, librarians, loans, reservations, and fines with clear ownership and multiplicity rules.
What is in this drawing
Read the decisions behind it.
01
Separate Book (metadata) from BookItem (physical copy) to allow multiple copies and track status per copy.
02
Use composition for Library-Book and Book-BookItem, aggregation/association for member loans and reservations, and dependency for fine generation.
Use this diagram when designing a library circulation system, integrating with an OPAC, or modeling inventory and loan lifecycle.
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