Try to model a simple Library system that has a number of shelves, and each shelf has a number of books that are arranged in a sorted order based on their title.
试着建立一个拥有一定数量书架的简单图书馆系统的模型，每一个书架拥有一些按其名字排序的书籍。
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Wal-Mart’s inventory-management system, called Retail Link, enables suppliers to see the exact number of their products on every shelf of every store at that precise moment.
There are, however, a large number of off-the-shelf solutions, many that are not even customized for IT information, that can just as conveniently be used for this purpose.