Solutions-8th-Ch06

Solutions-8th-Ch06 - Accounting Information Systems, 8e1...

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1 M M M Students (agent) Classes (resource) Registration (event) Accounting Information Systems, 8e 1 SOLUTIONS FOR CHAPTER 6 Discussion Questions DQ 6-1 What is a model? How is modeling a database or information system useful and important from a business or accounting perspective? ANS . Models are abstractions or simplifications of very complex phenomena, in our domain we model business processes. Appropriate models help us understand complex phenomena by showing us what is most important and by allowing us to disregard unnecessary details without losing valuable information. This is why it is important to choose your models carefully since by definition models are created by systematically ignoring certain aspects of a problem. Models don't have to be graphical. They can be verbal or mathematical. Some of the key models in this textbook are (1) the functional model of information systems discussed in chapter 1 (see Figure 1.3), (2) the REA model in Chapters 5 and 6; and (3) ‘the’ accounting equation or balance sheet model (Assets = Liabilities + Owners’ Equity). The last two are especially interesting because they illustrate how the same phenomenon can be modeled in two different ways. DQ 6-2 Discuss how you determine the placement of primary keys in relational tables to link the tables to each other. ANS. 1. Assign a primary key to every table. 2. Link the tables and determine their cardinalities (maximum) as 1:1, 1:M or M:N. 3. If 1:1, then you can transfer the primary key from either table to the other as the foreign or linking key; or you can combine the two tables into a single table. 4. If 1:M, transfer the primary key from the ‘1-table’ to the ‘M-table’ as the foreign key. 5. If M:N, then it will be necessary to create a new (third) relationship table between the two base tables. As a result, the M:N relationship will be split into two 1:M relationships, with the relationship table serving as the ‘M-table’ for both relationships. The relationship table will have a composite primary key consisting of the primary keys from the two base tables. It may also have other attributes. DQ 6-3 How can primary keys and the linking of tables in a relational database affect controls? ANS. Technology Application 6-1 points out two ways the primary keys and linking tables together helps an organization achieve its internal control objectives. First, when tables are well designed (or normalized) so that each table contains data only about a single entity (e.g., vendors), then it is easier to maintain data integrity, accuracy and consistency. Since producing accurate information (e.g., financial statements) is a primary internal
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2 Solutions for Chapter 6 control objective, having good data obviously helps the organization achieve this objective. The Technology Application also points out that primary keys and table linkages can act as controls on a more operational or technical level, e.g., preventing someone not in the customer table from renting a movie until they are entered in the
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Solutions-8th-Ch06 - Accounting Information Systems, 8e1...

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