Page 229 - Using MIS

Collaboration Exercise 5 197

and the copy to be checked out. Finally, consider what hap- a. Select identifiers for the ChoirMember and Work
pens when the user wants to find all copies of a particular entities. Justify your selection.
work: The user will have to examine the rows in each of four b. This design does not eliminate the potential for
spreadsheets for the four voice parts. data integrity problems that occur in the spread-
In fact, a spreadsheet is ill suited for this application. A sheet. Explain why not.
database would be a far better tool, and situations like this are c. Design a database for this data model. Specify key
obvious candidates for innovation. and foreign key columns.
5-5. Analyze the spreadsheet shown in Figure 5-29 and list 5-7. Figure 5-30b shows a second alternative data model
all of the problems that occur when trying to track the for the sheet-music-tracking problem. This alternative
assignment of sheet music using this spreadsheet.
shows two variations on the Work entity. In the second
5-6. Figure 5-30a shows a two-entity data model for the variation, an attribute named WorkID has been added
sheet-music-tracking problem. to Work_Version3. This attribute is a unique identifier

ChoirMember Work
LastName NameOfWork
FirstName Composer
Email Part
Phone CopyNumber
Part

(a) Data-Model Alternative 1
ChoirMember Work_Version2 Work_Version3
LastName NameOfWork WorkID
FirstName Composer NameOfWork
Email or Composer
Phone
Part

Copy_Assignment

Part
CopyNumber
(b) Data-Model Alternative 2

(Either Work_Version2 or
Work_Version3)

ChoirMember Copy
LastName Part
FirstName CopyNumber
Email
Phone
Part

Assignment

DateOut
Figure 5-30 DateIn
Data-Model Alternatives for the
Assignment of Sheet Music (c) Data-Model Alternative 3