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Last updated on 5/5/22

Create a UML Class Diagram for Your Database

Evaluated skills

  • Create a UML class diagram for your database
  • Question 1

    Which of these three statements is correct?

    • An instance defines the general shape of an object you want to represent in a database. You can use it to create many classes in the same shape

    • If the  Cat  and  Dog  classes inherit the  Animal  class, you can say that these two classes are instances of  Animal  .

    • If you store Ms. Smith’s labrador in a database whose conceptual model contains a  Dog  class, this labrador would be one instance of the  Dog  class.

  • Question 2

    An invoice has a total including tax, equal to the total excluding tax to which you add tax. The government determines the current tax rate. You decide to represent an invoice using an  Invoice  class, which has three attributes:

    • “totalIncTax”
    • “totalExTax”
    • “TaxRate” 

     

    Which of the following statements is false?

    • There is data redundancy if none of these attributes are considered derived attributes.

    • All three of these attributes are derived because you can calculate any of them from the other two.

    • If none of these attributes are derived attributes, there could be inconsistencies within the database. For example, if a person enters an invoice into the software with a “totalExTax = $1000,” “TaxRate = 5%,” and “totalIncTax = $1000”. When actually, the total including tax is $1050 ($1000 + 5% = 1050).

    • Because the total including tax is calculated using the total (excluding tax) and the tax rate, it would be best to consider the total including tax to be an attribute derived from the other two.

  • Question 3

    Imagine an online store selling products represented by a  Product  class. This class contains a  guarantee  attribute, which indicates the duration of the guarantee in months. Which of the following three domains is the most suitable for this attribute?

    • A whole number greater than or equal to 0 

    • A whole number

    • Text

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