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ObjectivesUnderstand the basic characteristics of object-oriented systems.Be familiar with the Unified Modeling Language (UML),V.2.0.

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Non-Object-Oriented…Process models

Based on behaviour and actionsData Models

Based on static (fixed) representations of data

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A “Simple” Process for Making Lunch

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Process Modelling:

Data Flow Diagrams

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Reading a DFD

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Data Modelling:

Entity-Relationship Diagrams (ERDs)

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What Is an ERD?A picture showing the information created, stored, and used by a business system. Entities generally represent people, places, and things of interest to the organization.Lines between entities show relationships between entities.

Copyright 2005 John Wiley & Sons, Inc. All rights reserved.PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design

Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

An ERD Example

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Entities and Instances

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Object-Oriented ApproachesCombine processes and dataAre more ‘natural’

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Basic Characteristics of Object Oriented Systems

Classes and ObjectsMethods and MessagesEncapsulation and Information HidingInheritancePolymorphism

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Helpful Hint….’Compile’C ClassesO Objects M Methods and MessagesP Polymorphism I Inheritance(Last, but not least)E Encapsulation

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Classes and ObjectsClass – Template to define specific instances or objectsObject – Instantiation of a classAttributes – Describes the objectBehaviours – specify what object can do

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Classes and Objects

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Methods and MessagesMethods implement an object’s behaviour

Analogous to a function or procedure

Messages are sent to trigger methods

Procedure call from one object to the next

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Messages and Methods

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Encapsulation and Information Hiding

Encapsulation combination of data and process into an entity

Information HidingOnly the information required to use a software module is published to the user

Reusability is the Key Pointan object is used by calling methods

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InheritanceSuperclasses or general classes are at the top of a hierarchy of classesSubclasses or specific classes are at the bottomSubclasses inherit attributes and methods from classes higher in the hierarchy

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Class Hierarchy

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Inheritance

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PolymorphismA message can be interpreted differently by different classes of objects

e.g. A ‘Create_Record’ message is essentially the same thing, but causes ‘Create_Patient_Record’ by a ‘Patient_Database’ object, or ‘Create_Doctor_Record’ by a ‘Healthcare_Staff_Database’ object

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Polymorphism & Encapsulation

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Benefits of the Object Approach

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The Unified Modelling Language, Version 2.0

Functional DiagramsStructure DiagramsBehaviour Diagrams

Developers Grady Booch Ivar Jacobson James Rumbaugh

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Functional DiagramsActivity Diagrams

Illustrate business workflowsUse-Case Diagrams

Capture business requirementsIllustrates interaction between system and environment

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Structure DiagramsClass diagrams

relationship between classesObject diagrams

Relationships between objects

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Behaviour DiagramsInteraction Diagrams ....

Sequence diagrams Show Time-based ordering and behaviour

of objects and their activitiesState Machines ...

Behavioural State Machines (Statechart diagrams)

Examines behaviour of one class/object

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Object Oriented Systems Analysis and Design• Use-case driven• Iterative and Incremental• Often associated with PHASED

Development (a RAD methodology)

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Basic Method for Development of Object Oriented Systems

Identifying business valueAnalyze feasibilityDevelop workplanStaff the projectControl and direct projectRequirements determinationFunctional modellingStructural modellingBehavioural modellingMoving on to design

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SummaryProcess oriented (Data flow diagrams) and Data oriented (Entity relationship diagrams)Basic characteristics of Object Oriented Systems Analysis and DesignIntroduction to Unified Modelling Language and the Unified Process