Transcript An Introduction to Object-Oriented Systems Analysis and

Slide 19.1
An Introduction to
Object-Oriented
Systems Analysis and Design
with UML and
the Unified Process
McGraw-Hill, 2004
Stephen R. Schach
[email protected]
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
CHAPTER 19
Slide 19.2
INTRODUCTION TO
DATABASE MANAGEMENT
SYSTEMS
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Overview






Files and Their Problems
Tables
Traditional Database Systems
Object-Oriented Database Systems
Database Design and the Unified Process
The Future of Object-Oriented Database
Management Systems
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.3
Definitions

Slide 19.4
Database
– A collection of data records organized to facilitate the
storage and retrieval of the data by information systems

Database management system
– The software that runs a database
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Files and Their Problems

The mailing list for STAMbury Philatelic Society
(STAMPS)

Version 1: Typewriter
– Data are volatile
– This approach is totally unacceptable
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.5
Files and Their Problems (contd)

Version 2: Computer files

Two independent programs
– Program A: Writes name and address data to disk
– Program B: Prints mailing labels from the file data
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.6
Files and Their Problems (contd)

Slide 19.7
Deployment diagram of a computer and its disk
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Files and Their Problems (contd)

Version 3: Program A needs to be modified
– Members resign
– Members change their names and addresses,
– New members join

Program A needs to be a CRUD program
–
–
–
–

Create
Read
Update and
Delete
Program B is unchanged
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.8
Files and Their Problems (contd)

Statechart for Version 3
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Slide 19.9
Files and Their Problems (contd)

Typical data used by Program B
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Slide 19.10
Files and Their Problems (contd)

Topical (or thematic) stamp collectors
– Collect stamps relating to a specific topic

STAMPS members collect stamps that depict
– Chess games
– Fictional detectives
– Elephants
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.11
Files and Their Problems (contd)
Slide 19.12

Version 4: STAMPS now wants to send out separate
mailings to members of the three topical groups

Alternative 1:
– Program A is changed to incorporate topical interests
– Program B is modified accordingly
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Files and Their Problems (contd)

Slide 19.13
The topical collecting interests of six members of
STAMPS
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Files and Their Problems (contd)

Slide 19.14
Alternative 2:
– Do not change Program A or Program B
– Divide the data file into three separate files,one for each
topical group
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Files and Their Problems (contd)

Separate files for
each topical group
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.15
Files and Their Problems (contd)

Slide 19.16
Problem 1:
– A mailing to all members of stamps can lead to duplication
or triplication
» Example: Ngaio Alleyn
– Redundant information
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Files and Their Problems (contd)

Slide 19.17
Problem 2:
– A change of address may require changes to more than
one file
» Example: Ngaio Alleyn
– Update anomaly
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Files and Their Problems (contd)

Slide 19.18
Problem 3:
– Deletion from a topical group may result in removal from
the STAMPS database
» Example: Dorothy Wimsey
– Deletion anomaly
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Tables

Slide 19.19
Membership list table incorporating membership
number
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Tables (contd)

Membership tables
for the three topical
groups
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.20
Tables (contd)

This solves all three problems

Problem 1:
Slide 19.21
– To send a mailing to all members, extract (unique) data
from the membership list table
– Program B requires minor changes to handle membership
numbers
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Tables (contd)

Slide 19.22
Problem 2:
– A change of address is made to the (unique) entry in the
membership list table
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Tables (contd)

Slide 19.23
Problem 3:
– A deletion from the membership table of a topical group
does not change the membership list table entry
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Tables (contd)

Slide 19.24
To print mailing labels for just the members of one
topical group, modify Program B to
– Read each membership number from the membership list
of that topical group, and
– Look up the corresponding name and address in the
membership list table
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Tables (contd)

The information system can be extended to
incorporate additional information
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.25
Traditional Database Systems

Slide 19.26
Almost all traditional database management
systems are relational
– Data are stored in tables
– The primary key labels primary records
– The primary key can be used to label records in other
tables—foreign key
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Traditional Database Systems (contd)

Slide 19.27
The software of the STAMPS information system is
explicitly written to manage the data
– Program A and Program B
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Traditional Database Systems (contd)

Information systems use a database management
system for
– Writing of data to disk and
– Retrieval of data from the disk

Slide 19.28
Examples:
– Mainframe: DB2, Oracle, Informix, Sybase
– Personal computers: Microsoft Access
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Traditional Database Systems (contd)

Database instructions are embedded within the
source code, frequently written in COBOL
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.29
Traditional Database Systems (contd)

Slide 19.30
Finding the address of policyholder Joe Soap can be
achieved with the database instruction
retrieve address of policyHolder
where firstName of policyHolder is "Joe"
and lastName of policyHolder is "Soap"
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Traditional Database Systems (contd)

Slide 19.31
The COBOL code first passes through a precompiler
– To convert the instructions to the database management
system into COBOL

The resulting all-COBOL program is then compiled,
linked, and run in the usual way

When the database instruction is executed
– The database management system searches the
database for Joe Soap, and
– Returns his address to the COBOL program
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Traditional Database Systems (contd)

Execution of the database instruction
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Slide 19.32
Traditional Database Systems (contd)

Database instructions can be embedded within
many traditional programming languages
– Including C and COBOL

Typical database instructions include
–
–
–
–
Retrieve
Insert
Delete, and
Update
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 19.33
Traditional Database Systems (contd)
Slide 19.34

The database management system manages the
database itself

The programmer writes code to
– Invoke the database management system, and
– Provide it with data it needs
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Object-Oriented Database Systems
Slide 19.35

A company with a traditional database management
system is unlikely to use object-oriented database
management systems for some time

They are still too complex
– An extensive background in object-oriented database
theory is needed
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.36

When an existing database is converted into an
object-oriented database
– The existing traditional information systems cannot access
the new database
– They have to be totally rewritten, at enormous cost
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.37

Solution 1: Two databases
– The one traditional, and
– The other object-oriented
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Object-Oriented Database Systems (contd)
Slide 19.38

However, a major reason for using a database is to
have just one copy of each record

Two databases means having
– Two copies of all data, and
– Two versions of every new information system

This is totally ridiculous
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.39

Solution 2: A hybrid system
– An object-oriented information system interfacing with a
traditional database management system
– Instructions are embedded in C++ or Java code
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.40

The database management system must
– Manage the database (as before), and
– Perform conversions from traditional to object-oriented
systems, and vice versa
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.41

When writing data to the traditional database it must
– Extract the data from an object
– Convert the data into a record, and
– Write the record to the traditional database

After retrieving a record from the traditional
database, it must
– Insert the record into an object
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Database Design and the Unified Process
Slide 19.42

Using a database management system is easy, but

Designing a database requires specialized skills
– Including detailed knowledge of the theory of databases
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Database Design and the Unified Process
Slide 19.43

The Information Systems curriculum usually
includes at least one course on databases
– This material is not included in the Systems Analysis and
Design course

Similarly
– The Unified Process does not include database design
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Future of O-O Database Management Systems
Slide 19.44

Object-oriented database management systems will
become as easy to use as traditional database
management systems

It will still be too expensive to convert existing
databases and information systems to the objectoriented paradigm
– However, new information systems will be written using
the object-oriented paradigm, but will interface with the
traditional database
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Future of O-O Database Management Systems
Slide 19.45

New companies will use the object-oriented
paradigm for both
– Its information systems, and
– Its database management system
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.46

Legacy systems are the biggest obstacle to the
widespread utilization of object-oriented database
management systems
– Just as they are to object-oriented information systems in
general
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
Object-Oriented Database Systems (contd)
Slide 19.47

The object-oriented paradigm is the current choice
for the development of new information systems
– This will lead to the adoption of object-oriented database
systems in the future
Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.