Attaching section 7.1.1 for reference:

1 Section 7.1.1 discusses the impact analysis in the point-of-sale system. For each of the following software changes, determine the estimated impact set: a. Keep detailed sale records such as item sold and date/time of sale. b. Support multiple items per transaction. c. Expand cash payment to include cash tendered and return change. d. Implement payment by a check. 7.1.1 Example: Point-of-Sale Software Program Software systems consist of tightly interdependent software classes. When a change appears in one of the classes, it may trigger secondary changes in interacting classes. An example is a variant of a point-of-sale program that supports a small store and keeps track of an inventory of items by item name, price, tax, available quantity, cashiers who are authorized to sell in the store, and so forth. The Unified Modeling Language (UML) class diagram for this program is in Figure 7.4. The classes in the program are Store, which is the top class of the application; class Cashiers, which contains a list of cashiers; class Inventory, which supports the inventory for the store; class Item, which contains data of a specific item that is being sold in the store; and class Price, which contains the price of an item. The code of class Price assumes that there is only a single price for every item, and as a result, class Price is very simple; it contains just one integer for the price and getprice() and putprice() methods that return and set the price of the item, respectively. A software change to be done is described by the following change request: "Support price fluctuations; the users of the program should be able to set prices of items in advance and be able to change the item prices on selected dates. For Figure 7.4 Small point-of-sale program. Figure 7.5 The initial and estimated impact set of the price fluctuations. example, there can be sales periods where on certain dates the price is lower, while after these dates it returns to the previous level." This change requires an overhaul of the class Price that adds a new functionality that deals with the price changes on specific dates. As a result, getPrice() and putPrice() methods will have an extra parameter "date" that the clients of class Price have to use when calling these methods. Classes Item and Inventory will be affected and become members of the estimated impact set. Figure 7.5 contains the dark-shaded class Price, where the change starts and which constitutes the initial impact set, and the light-shaded estimated impact set