That includes the regular information about a
book, but also information about which instances are available, which are borrowed, and at
which libraries they are.
??? Operation ID: 10
??? Request: BookDescriptionID:INTEGER
??? Response: BookDescriptionID:INTEGER Title:STRING
??? Authors:LIST
ISBN:STRING
??? Instances:LIST
Add Book Instance
To add a new book instance, call this operation with the book description ID to add, and the
ID of the library to add it to.
??? Operation ID: 4
??? Request: LibraryID:INTEGER BookDescriptionID:INTEGER
??? Response: InstanceID:INTEGER
CHAPTER 13 ?– JRUBY AND MESSAGE-ORIENTED SYSTEMS 233
Remove Book Instance
This operation removes a book instance from the database.
??? Operation ID: 5
??? Request: InstanceID:INTEGER
??? Response: Nothing
Lend Book Instance
To lend a specific book instance to someone, call this method. The legacy system doesn??™t keep
track of who lends what; it just keeps track of whether a book instance is lent or not. You can
call this operation on an already lent book; that makes no difference. So, the user of these
operations should do all checking that needs to be done.
??? Operation ID: 6
??? Request: InstanceID:INTEGER
??? Response: Nothing
Return Book Instance
This operation is exactly like lending a book, but the inverse. As with lending, the legacy
system doesn??™t check anything, and you can return a book instance that hasn??™t been lent to
anyone.
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