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Figure 5-56
Air Compressor
Specifications
B.
Figure 5-56 shows a different model for the compressor data. Explain the entities,
their type, the relationship, its type, and its cardinality. How well do you think this
model fits the data shown in Figure 5-56?
C.
Compare your answer in part A with the model in Figure 5-57. What are the essen-
tial differences between the two models? Which do you think is better?
D.
Suppose you had the job of explaining the differences in these two models to a
highly motivated, intelligent end user. How would you accomplish this?
5.60
Figure 5-58 shows a listing of movie times at theaters in Seattle, Washington. Using the
data in this figure as an example, do the following:
a.
Create a model to represent this report using the entities MOVIE, THEATER, and
SHOW_TIME. Assume that theaters may show multiple movies. Although this re-
port is for a particular day, your data model should allow for movie times on differ-
ent days as well. Specify the identifier of the entities and their attributes. Name the
relationships and the type and cardinality of all relationships. Explain which cardi-
nalities you can logically deduce from Figure 5-58 and which need to be checked
out with users. Assume that distance is an attribute of THEATER.
B.
This report was prepared for a user who is located near downtown Seattle.
Suppose that it is necessary to produce this same report for these theaters, but for
a user located in a Seattle suburb, such as Bellevue, Renton, Redmond, or Tacoma.
SS_COMPRESSOR
Figure 5-57
Alternative Model for
Compressor Data
AIR_PERFORMANCE_TYPE
Model
AirPerformance
HP
Tank Gal
ApproxShipWeight
Length
Width
Height
PumpRPM
CFMDisp
Del'dAir
2
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