The scenario
A public library needs to model branch operations, catalog metadata versus physical copies, member borrowing, reservations, and staff roles.
What is in this drawing
Read the decisions behind it.
01
Modeled Person as an abstract base class shared by Member and Librarian.
02
Separated Book (catalog metadata) from BookCopy (physical item) to handle multiple copies per branch.
03
Used composition from Library to Branch and Book to BookCopy, with associations for loans, reservations, and staff assignments.
Reuse when designing a domain model for library circulation, branch inventory, or member services that involve physical items and multiple user roles.
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