object-oriented methodologyobject modelsuse case modelingunified modeling languagethe data dictionarythe cornucopia caseportfolio project

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section IIAnalysis

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

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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

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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

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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

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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

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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

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The Object Model and the Six CIS Components

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PeopleProceduresDataHardwareSoftwareNetworks

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

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Anatomy of an Object

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•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

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Object Model Symbols

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

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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

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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

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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

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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

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Silhouette’s UML Use Case Diagram

Silhouette’s UML Class Diagram

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Silhouette’s UML Interactive sequence Diagram

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Silhouette’s UML Statechart Diagram

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Inflatable Labor Charges

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ThinkingCritically

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

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Form Symbols

multiple entries { } permitted

optional entry [ ]

key field underline

data structure =composition

attribute +separator

Illustrated Data Dictionary Form and Symbols

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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.

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THE CORNUCOPIA CASE

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Cornucopia Existing System Object Model

Chapter Summary (1/3)

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• 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)

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• Objects are characterized by their attributes and behaviors

• Objects communicate with one another through messaging

Chapter Summary (3/3)

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• 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