section II Analysis

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18 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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object
-
oriented methodology

object models

use case modeling

unified modeling language

the data dictionary

the cornucopia case

portfolio project



Systems Analysis and Design

for the Small Enterprise

section II

Analysis

Chapter Objectives

When you complete this chapter you will be able to:


Differentiate between object
-
oriented and
traditional methodologies


Identify objects and construct an elementary
object model


Identify the elements in a use case model


Identify the elements in four of the most
common UML models


Define, construct, and maintain data dictionaries

2

Object
-
Oriented Methodology


Object
-
oriented systems analysis and design
(OOSAD) evolved to accommodate the
increasing popularity of object
-
oriented
programming languages



If you plan to implement your design with
object
-
oriented development tools, you should
seriously consider using OOSAD



As the name implies, OOSAD revolves around
objects

3

Object
-
Oriented Methodology


Information system objects derive their
definition from our understanding of real
-
world objects



Just as real
-
world objects are organized into
classifications, enterprise objects are
members of a class



While a specific object is distinguished by its
particulars, it inherits its general makeup
from its class



4

Object
-
Oriented Methodology


By definition, a class embodies two important
information processing concepts:


Data attributes


Behaviors



After enterprise objects are created from their
class blueprint, their data attributes are
assigned values and their behaviors are
tailored to fit their specific circumstance



Objects interact with one another through a
messaging system




5

Object
-
Oriented Methodology


The object
-
oriented methodology involves
familiar phases: analysis, design, and
implementation


Analysis: Identify the classes from which enterprise
objects are created and the interactions between
these classes



Design: Refine class definitions and interactions
based on the requirements of the new information
system



Implementation: Create a working information
system using object
-
oriented languages and tools



6

Object Models




In the OOSAD methodology, the object
model serves the same purpose as do the
DFD and ERD in the traditional SDLC
methodology



The object model is focused on data and
software, showing classes and class
interactions


7

The Object Model and the Six CIS Components

8

People

Procedures

Data

Hardware

Software

Networks

Object


Class


Attributes


Methods

Object Models



Object Identification:



Use case modeling is the preferred technique
for identifying enterprise objects



Another way to identify classes is to use the
DFD and ERD models as a springboard, where
each of the DFD’s data stores and ERD’s
entities are potential classes



9

Anatomy of an Object

10


Class:

a two
-
part abstraction (attributes and methods) of
a real
-
world person, place, thing, or activity


Instance:

a specific object created from the class
blueprint


Encapsulation:

describes the enveloping, membrane
-
like
environment in which an object exists


Messages:

means by which objects communicate with
each other


Polymorphism:

allows a method to behave differently
when encapsulated in different classes


Inheritance:

imprints class definitions on new
generations of the class


Class relationships:

describes the way classes interact
with one another


TECHNOTE 5
-
1

11

Object Model Symbols

Reference Figure 5
-
2: Silhouette Sea Charter’s Object Model

12

Silhouette Sea Charter’s Object Model

This aggregate relationship allows
for one or more customers to
signup for the same charter

This specialization relationship
indicates that there are two
subsets of the Boat class

13

Comparing Silhouette’s Object Model and Data Model

Object Model

Data Model

Use Case Modeling


Use case modeling provides a systematic way
to identify objects



A use case is a detailed description of what
happens when someone or something
interacts with the information system



The nouns used to title the use case scenarios
provide a basis for object identification



The interactions between use cases provide
the basis for defining the relationship between
the objects underlying class

14

Unified Modeling Language




The Unified Modeling Language (UML) has
emerged as the generally accepted modeling
standard for object
-
oriented methodologies
and techniques



Four of the numerous UML diagrams serve the
same function as the traditional DFD, ERD,
and walk
-
through models:


Use case diagram


Class diagram


Interaction diagrams


Statechart diagrams



15

16

Nine UML Modeling Diagrams

Class Diagram

Object Diagram

Use Case Diagram

Interactive (Sequence) Diagram

Interactive Collaborative Diagram

Statechart Diagram

Activity Diagram

Component Diagram

Deployment Diagram

17

Silhouette’s UML Use Case Diagram

Silhouette’s UML Class Diagram

18

Silhouette’s UML Interactive sequence Diagram

19

Silhouette’s UML Statechart Diagram

20

Inflatable Labor Charges

21

Thinking

Critically

What action would you recommend if
you discovered that your most
talented analyst had consistently
inflated the labor hours charged to a
project?


The Data Dictionary


A data dictionary is an ordered catalog of data
elements and their definitive characteristics



22


Form Symbols


multiple entries { }

permitted


optional entry [ ]


key field
underline


data structure =

composition


attribute +

separator

Illustrated Data Dictionary Form and Symbols

23

Type:
data store

Element Name:

customer

Description:
customer master file

Contents:
customer =
custid
+


name+


address+


phone

Usage Cross
-
Reference:
DFD, USD,
ERD, system flowchart

Storage reference:
customer.dbf

The analysts do not intend to use an object
-
oriented programming language to
implement the new system. Even the
objectlike features of 4Gl software do not
require object identification or use case
modeling.


Cornucopia’s object model is derived from
the ERD.

24

THE CORNUCOPIA CASE

25

Cornucopia Existing System Object Model

Chapter Summary (1/3)

26



The object model is an alternative to the
traditional SAD methodology



It is important to understand the object model,
even if the analyst does not intend to use
object
-
oriented development tools



Objects are created from a class blueprint




Chapter Summary (2/3)

27


Objects are characterized by their attributes
and behaviors



Objects communicate with one another
through messaging

Chapter Summary (3/3)

28


The Unified Modeling Language (UML)
provides a collection of modeling tools for
OOSAD


Use case diagram


Class diagram


Interaction diagrams


Statechart diagram



The data dictionary provides a systematic
procedure to keep track of the names,
definitions, associates, and existing or
proposed uses of data