For a library, the entity type HOLDING has four sub-types: BOOK, AUDIO BOOK, DVD, and SOFTWARE. Draw a separate EER diagram segment for each of the following situations: a. At a given time, a holding must be exactly one of these subtypes. b. A holding may or may not be one of these subtypes. However, a holding that is one of these subtypes cannot at the same time be one of the other subtypes. c. A holding may or may not be one of these subtypes. On the other hand, a holding may be any two (or even four) of these subtypes at the same time.
ENHANCED CHEN METHODOLOGY
EER MODEL
3-25
For a library, the entity type HOLDING has four sub-types: BOOK, AUDIO BOOK, DVD, and
SOFTWARE. Draw a separate EER diagram segment for each of the following situations:
a. At a given time, a holding must be exactly one of these subtypes.
b. A holding may or may not be one of these subtypes. However, a holding that is one of
these subtypes cannot at the same time be one of the other subtypes.
c. A holding may or may not be one of these subtypes. On the other hand, a holding may
be any two (or even four) of these subtypes at the same time.
d. At a given time, a holding must be at least one of these subtypes.
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A bank has three types of accounts: checking, savings, and loan. Following are the attributes for
each type of account:
CHECKING: Acct No, Date Opened, Balance, Service Charge
SAVINGS: Acct No, Date Opened, Balance, Interest Rate
LOAN: Acct No, Date Opened, Balance, Interest Rate, Payment
Assume that each bank account must be a member of exactly one of these subtypes. Using
generalization, develop an EER model segment to represent this situation using the traditional
EER notation, the Visio notation, or the subtypes inside supertypes notation, as specified by
your instructor. Remember to include a subtype discriminator.
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