Databases Reference
In-Depth Information
set of program segments is stored with the data and is the only code allowed to
update that particular data. Today, object-oriented database management systems
have largely given way to the incorporation of these object-oriented features rated
into mainstream relational database management systems.
KEY TERMS
Abstract data type
Aggregation
Class
Class diagram
Complex relationships
Encapsulation
Generalization/specialization
Inheritance
Message
Method
Object
Object class
Object-oriented data modeling
Object-oriented database
Object/relational database
Operation
Polymorphism
Procedure
Unified Modeling Language (UML)
QUESTIONS
1. Name and briefly describe three deficiencies in the
relational database model.
2. In object-oriented terminology, what is an object?
What is a class?
3. Describe the advanced relationship known as
''generalization.'' What are its benefits?
4. Describe how attributes are inherited in a general-
ization hierarchy.
5. What is an ''operation?'' Can operations be
inherited? What is polymorphism?
6. Describe the advanced relationship known as
''aggregation.'' What are its benefits?
7. What is encapsulation in object-oriented databases?
What are its benefits?
8. What is an abstract data type (ADT)? What is the
significance of a database system that is capable of
creating ADTs?
9. What is an object/relational database management
system? What are its advantages?
EXERCISES
1. Draw an object-oriented class diagram, including
traditional unary, binary, and ternary relationships,
as well as generalization and aggregation relation-
ships as needed, to represent the following business
environment. Include all of the attributes and oper-
ations listed in the description.
The Houston, TX, city government wants to
develop an information system to keep track of
all the buildings in the city for both taxation and fire
department dispatch purposes. The city will track
the address, year built, and owner of record of every
building. It will also record the station number,
address, and telephone number of each fire station.
Each fire station has primary responsibility for a
given set of buildings.
There are four types of buildings: single-family
homes, apartment buildings, stores, and office
buildings. The city wants to record the number
of apartments in each apartment building, and the
type of goods and annual sales volume of each
store. It wants to record the number of floors in
each office building. It must also keep track of
the companies in each office building. An office
building can have several or many companies in it;
a company can have offices in several buildings.
Each company has a name, telephone number, and
unique tax identification number. The city alsowants
to store the number of square feet that a particular
company occupies in a particular office building.
Single-family homes are made up of three parts: the
house itself, a garage, and a shed. The city wants to
keep track of the number of bedrooms, number of
baths, and total floor space in the house, the capacity
of the garage in number of cars, and the capacity of
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