ObjectOriented Modeling Using Modified Modeling Language UML Outline

Object-Oriented Modeling Using Modified Modeling Language (UML)

Outline • • • Unified Modeling Language Principles and Concepts Modeling Relations and Structures Modeling Dynamic Behavior Modeling Requirements with Use Cases 2

What is a Model? A model is a simplification of reality. A model may provide – blueprints of a system – Organization of the system – Dynamic of the system 3

Why We Model “A successful software organization is one that consistently deploys quality software that meets the needs of its users. An organization that can develop such software in a timely and predictable fashion, with an efficient and effective use of resources, both human and material, is one that has sustainable business. ” 4

Why We Model • Model is built to – Communicate the desired structure and behavior of the system – Visualize and control the system’s architecture – Better understand the system that being built – Manage risk – Expose opportunities for simplification and reuse 5

Why We Model • We build models so that we can see and better understand the system we are developing. 6

Importance of Modeling • Models help us – to visualize a system as it is or as we want it to be. – to specify the structure or behavior of a system. – in providing a template that guides us in constructing a system. – in providing documenting the decisions we have made. 7

Principles of Modeling • The choice of what models to create has a major influence on how a problem is approached and how a solution is shaped. • Every model may be expressed at different levels of precision. • The best models are connected to reality. • No single model is sufficient. Every nontrivial system is best approached through a small set of nearly independent models. 8

Objected-Oriented Modeling • Two most common ways in modeling software systems are – Algorithmic • Procedures or functions – Object oriented • Objects or classes 9

What is UML? • UML is a language for – – Visualizing Specifying Constructing Documenting 10

Building Blocks of UML • Things -- abstraction • Relations -- tie things together • Diagrams -- group interesting collections of things 11

Principles and Concepts • Objects and Classes • Principles 12

Objects and Classes Interpretation in the Real World Interpretation in the Model Object An object is a thing that can be distinctly identified. An object has an identity, a state, and a behavior. Class A class represents a set of objects with similar characteristics and behavior. This objects are called the instances of the class. A class characterizes the structure of states and behaviors that are shared by all instances. 13

Objects • Each of object has a unique identity. • The state of an object is composed of a set of fields (data fields), or attributes. • Each field has a name, a type, and a value. • Behaviors are defined by methods. • Each method has a name, a type, and a value. • Each method may or may not return a value. • Features are a combination of the state and the behavior of the object. 14

Properties of Objects • Two objects are equal if their states are equal. • Two objects are identical if they are the same objects. • The values of the fields are mutable. • Methods that do not modify the state of the object are called accessors. • Methods that modify the state of the object are called mutators. • Objects can be mutable or immutable. 15

Classes • A class defines a template for creating or instantiating its instances or objects. • A class is a description of a set of objects that share the same attributes, operations, relationships, and semantics. 16

Classes • A class defines -- – the names and types of all fields – the names, types, implementations of all methods • The values of the fields are not defined or fixed in the class definition. • The values of the fields are mutable. • Each instance of the class has its own state. • Different instances of the class may have different states. • The implementations of methods are defined in the class definition and fixed for a given object. • Values of methods are immutable 17

Example Class name: Point class Point { Fields: x, y int x, y; Method: move public void move (int dx, int dy){ // implementation } 18

UML Notation for Classes Class. Name field 1 … fieldn method 1 … methodm The top compartment shows the class name. The middle compartment contains the declarations of the fields of the class. The bottom compartment contains the declarations of the methods 19

Field Declaration • The name of the field is required in the field declaration. • Field declaration may include: [Visibility][Type]Name[[Multiplicity]][=Initial. Value] [Visibility]Name[[Multiplicity]][: Type][=Initial. Value] • Visibility or accessibility defines the scope: – Public -- the feature is accessible to any class – Protected -- the feature is accessible to the class itself, all the classes in the same package, and all its subclasses. – Package -- the feature is accessible to the class itself and all classes in the same package. – Private -- the feature is only accessible within the class itself. 20

Visibility syntax in Java and UML Visibilty Java Syntax UML Syntax public + protected # package private ~ private 21

Examples Java Syntax UML Syntax Date birthday Birthday: Date Public int duration = 100 +duration: int = 100 Private Student students[0. . MAX_Size] -students[0. . MAX_Size]: Student 22

Method Declaration • The name of the method is required in the method declaration. • Method declaration may include: [Visibility][Type]Name([Parameter, . . . ]) [Visibility]Name([Parameter, . . . ])[: Type] • Each parameter of a method can be specified by -- Type Name 23

Examples Java Syntax UML Syntax void move(int dx, int dy) ~move(int dx, int dy) public int get. Size() +int get. Size() 24

Example Point private int x private int y -x: int -y: int +move(dx: int, dy: int) Point public void move(int dx, int dy) x y move() 25

UML Notation for Object. Name : Class. Name field 1 = value 1 … fieldn = valuen The top compartment shows the object name and its class. The bottom compartment contains a list of the fields and their values. object. Name -- object. Name whose class is of no interest : Class. Name -- anonymous object of Class. Name which can be identify only through its relationship with other object. 26

Examples P 1: Point x = 0 y = 0 P 1: Point x = 24 y = 40 Point p 1 = new Point(); p 1. x = 0; P 1. y = 0; Point p 1 = new Point(); p 1. x = 24; P 1. y = 40; 27

Message Passing or Method Invocation • Objects communicate with one another through message passing. • A message represent a command sent to an object -- recipient • A message consists of the receiving object, the method to be invoked and the arguments to method. 28

Example Recipient p 1. move(10, 20) Method p 1 move() Arguments (10, 20) 29

Packages • Package name are in lower case -Java. awt. event javax. swing. * • Packages that will be widely used should be named as the reverse of the internet domain as the prefix of the package name EDU. emporia. mathbeans. Math. Table EDU. emporia. mathtools. * 30

UML notation of packages 31

Principles • Modularity: – alleviate complexity of large-scale systems • Abstraction: – separating the essential from the non-essential characteristics of an entity • Encapsulation: – Information hiding • Polymorphism: – Portability • Levels of Abstraction: – Organization of classes and interfaces 32

Principle of Modularity • A complex software system should be decomposed into a set of highly cohesive but loosely coupled modules. • The basic for decomposition are cohesion and coupling. – Cohesion -- functional relatedness of the entities within modules. – Coupling – inter-dependency among different modules. • Each module is relatively small and simple • Interactions among modules are relatively simple • hierarchical 33

Principle of Abstraction • The behaviors or functionalities should be precisely characterized as contractual interface which captures the essence of the behavior. • The complexity of the module is hidden from the clients. 34

Principle of Encapsulation • The implementation of a module should be separated from its contractual interface and hidden from the clients of the module. • Information hiding 35

Principle of Polymorphism • Ability to interchange modules dynamically without affecting the system. • refers to a contractual interface with multiple interchangeable implementation 36

Modeling Relationships and Structures • A class diagram consists of – A set of nodes that represent classes and interfaces – A set of links represent relationships among classes • Class diagrams can be used to model: – Inheritance -- extension and implementation – Association -- aggregation and compostion – Dependency 37

Inheritance • Define a relationship among classes and interfaces • Inheritance model -- the is-a(n) relationship 38

Example 39

Principle of Levels of Abstraction • Abstractions can be organized into different levels. • Higher level is more general 40

Association • Association represents binary relationship between classes Student advisee * * enroll * Course * teach 1 adviser 1 Faculty 41

Aggregation and Compositon • Aggregation is a special form of association – Has-a or part-whole relationship • Composition is a stronger form of aggregation 42

Example University 1 * College 1 * Department 1 * Student 1 1 1 Member-of 1. . * Chairman-of Faculty 43

Dependency • Dependency is a relationship between entities such that the properation of one entity depends on the presence of the other entity, and changes in one entity would affect the other entity. 44

Example Course. Schedule Registrar void add. Course(Course. Schedule a, Course c) void remove. Course(Course. Schedule Course find. Course(String title) void enroll(Course c, Student s) void drop(Course c, Student s Course Student 45

Modeling Dynamic Behavior • Sequence diagram – Depict object interaction by highlighting the time ordering of method invocation 46

Example 47

Modeling Dynamic Behavior • State diagram – Depict the flow of control using the concepts of state and transitions – Labels of transitions are in the form: [Event-List][[Guard]][/Action] - Entry action and exit action entry/Action 1 exit/Action 2 48

Graphical notations 49

Modeling Dynamic Behavior • Nested state diagram – Composite of state diagrams 50

Example talk 51

Modeling Requirements with Use Cases • Use cases describes the externally observable behavior of system functions in the form of interactions between the system to be developed and the external entities -- Actors. • Actors may represent roles played by users of the system or other systems. • Consist of a name and scenarios • One of scenarios is the main scenario 52

Use Case Diagram • Consist of: – Use cases – Actors – Relationships among actors and use cases 53

Extension relationships among actors 54

Dependency relationships among use cases 55

Case Study: An E-Bookstore • Problem requirements • Program specifications • Object models – Identifying classes – Identifying the features of classes -states and behaviors – Identifying relationships among classes – inheritance and interfaces. 56

Requirements • Allow customers to browse and order books, music CDs, and computer software 57

Specifications • Provide information on the books, CDs, and software • Provide a functionality for customers registration as well as updating customer’s information • Provide a functionality for ordering and shipping • Provide a functionality for updating inventory 58

Register Customer Logon Manager Manage catalog Shop Catalog Manager Manage Acount System administrator Process order Inventory manager 59

End of Lecture 6 60