object-oriented methodology

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section II Analysis
for the Small Enterprise
Systems Analysis and Design
object-oriented methodology object models use
case modeling unified modeling language the data
dictionary the cornucopia case portfolio project
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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
Object Class Attributes Methods
People Procedures Data Hardware Software Networks
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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 DFDs data stores and ERDs entities are
  potential classes

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Anatomy of an Object
TECHNOTE 5-1

• 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

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Object Model Symbols
Reference Figure 5-2 Silhouette Sea Charters
Object Model
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Silhouette Sea Charters 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 Silhouettes Object Model and Data Model
Object Model
Data Model
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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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Silhouettes UML Use Case Diagram
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Silhouettes UML Class Diagram
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Silhouettes UML Interactive sequence Diagram
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Silhouettes UML Statechart Diagram
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Inflatable Labor Charges
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?

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The Data Dictionary

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

Form Symbols multiple entries
permitted optional entry key field
underline data structure
composition attribute
separator
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Illustrated Data Dictionary Form and Symbols
Element Name customer
Type data store
Description customer master file
Contents customer custid
name
address
phone
Usage Cross-Reference DFD, USD, ERD, system
flowchart
Storage reference customer.dbf
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THE CORNUCOPIA CASE

• 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.
• Cornucopias object model is derived from the ERD.

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Cornucopia Existing System Object Model
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Chapter Summary (1/3)

• 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

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Chapter Summary (2/3)

• Objects are characterized by their attributes and
  behaviors
• Objects communicate with one another through
  messaging

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Chapter Summary (3/3)

• 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

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