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Introduction to Object Orientation System Analysis and Design

Introduction to Object Orientation System Analysis and Design. Objectives. Understand the basic characteristics of object-oriented systems. Understand the object orientation notation Understand how to analyze and design with OO paradigm. What’s Object Orientation?.

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Introduction to Object Orientation System Analysis and Design

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  1. Introduction to Object Orientation System Analysis and Design

  2. Objectives • Understand the basic characteristics of object-oriented systems. • Understand the object orientation notation • Understand how to analyze and design with OO paradigm

  3. What’s Object Orientation? • A new technology based on objects and classes • A paradigm (way of thingking) to organize software as a collection of discrete objects that incorporate both data and process. • An abstraction of the real world based on objects and their interactions with other objects.

  4. Basic Characteristic (1) Classes and Objects • OO focus on capturing structure and behaviour in little modules that encompass both data and process. These modules are known as OBJECTs. • Class is a general template we use to define and create specific instances or objects. • An object is an instantiation of a class. • Each object has attributes (describe the object) and behaviors (what an object can do).

  5. Class Car • Attributes • Model • Location • #Wheels = 4 • Operations • Start • Accelerate <<instanceOf>> <<instanceOf>> <<instanceOf>>

  6. Basic Characteristic (2) (2) Methods and Messages • Methods implement an object’s behaviour • In other languages, method is known as procedure or function. • A message is a function or procedure call from one object to another object.

  7. Basic Characteristic (3)

  8. Basic Characteristic (4) (3) Encapsulation and Information Hiding • Encapsulation : how to wrap process and data into a single entity. • Only the information required to use a software module is published to the user. Exactly how the module implements the required information is unnecessary.

  9. Basic Characteristic (5) (4) Inheritance • Is a mechanism to create a class from other class. • Related terms : superclass and subclass • Subclass inherit the appropriate attributes and methods from its superclass. • Avoid repeating of writing attributes or methods. • The relationship between the class and its superclass is known as the A-Kind-Of relationship.

  10. Basic Characteristic (6)

  11. (5) Polymorphism and Dynamic Binding • Polymorphism : the same message can be interpreted differently by different classes of objects. • For example : sent message “draw” to an circle object, a square object, and a triangle object will make a different result. • Dynamic Binding : determining the exact implementation of a request based on both the request (operation) name and the receiving object at run-time

  12. Various Methodologies • Shlaer/Mellor methods (Shlaer-1988) • Coad/Yourdon methods (Coad-1991) • Booch methods (Booch-1991) • OMT methods (Rumbaugh-1991) • Wirfs-Brock methods (Wirfs-Brock-1990) • OOSE Objectory methods (Jacobson-1992) • Unified Modelling Languages (UML-1997)

  13. Object Oriented Notation Guide

  14. Class and Object • Class • Instantiation relationship • Object instance Class name Attributes Methods Class Name Class Name

  15. Generalization and Inheritance

  16. Aggregation • Aggregation 1 • Aggregation 2

  17. Association • Association • Multiplicity of association

  18. Ternary Association

  19. Object oriented analysis and design

  20. Analysis and Design Process • Problem statement • System architecture • Object modelling • Identifying object classes • Preparing a data dictionary for classes • Identifying association • Identifying attributes • Refining with inheritance • Grouping classes into model • Dynamic modelling • Functional modelling

  21. Problem statements

  22. Problem Statement • Requirements statement • Problem scope • What’s needed • Application context • Assumptions • Performance needs

  23. Example : ATM Network

  24. System Architecture

  25. Identifying Object Classes

  26. Example : ATM Network

  27. Preparing a Data Dictionary

  28. Example • Account : a single account in a bank against which transactions can be applied. Account may be of various types, at least checking or savings. A customer can hold more than one account. • Bank : A financial institution that holds accounts for customers and that issues cash cards authorizing access to accounts over the ATM network. • ATM : … • Bank Computer : …. • Customer : … • etc

  29. Identifying Associations

  30. Example

  31. Identifying Attributes

  32. Example

  33. Refining with Inheritance • This step is to organize classes by using inheritance to share common structure • Inheritance can be added in two directions : • Bottom Up ： By generalizing common aspect of existing classes into a superclasses • By searching for classes with similar attributes, associations, or operations • For each generalization, define a superclass to share common features • Top Down ： By refining existing classes into specialized subclasses

  34. Example

  35. Grouping Class into Modules • A module is a set of classes that captures some logical subset of entire model • For example: a model of computer operating system might contain modules for process control, device control, file maintenance, and memory management

  36. Example • Tellers : Cashier, Entry Station, Cashier Station, ATM • Account: Account, Cash Card, Card Authorization, Customer, Transaction, Update, Cashier Transaction, Remote Transaction • Banks: Consortium, Bank

  37. Dynamic model

  38. Dynamic Model • The dynamic model shows the time-dependent behavior of the system and the objects in it. • Begin dynamic analysis by looking for event, externally visible stimuli and responses. • The dynamic model is important for interactive systems, but insignificant for purely static data repository, such as database.

  39. The following steps are performed in constructing a dynamic model : • Prepare scenarios of typical interaction sequences • Identify events between objects • Prepare an event trace for each scenario • Build a state diagram • Match events between objects to verify consistency

  40. Example

  41. Functional model

  42. Functional Model • The functional model shows how values are computed, without regard for sequencing, decisions, or object structure • The functional model shows which values depend on which other values and the functions that relate them • Data flow diagrams are useful for showing functional dependencies

  43. Example

  44. Object Orientation Implementation

  45. Implementation Process • Class Definition • Creating Objects • Calling Operations • Using Inheritance • Implementing Association

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