UML and Patterns Dr Zhen Jiang West Chester

UML and Patterns Dr. Zhen Jiang West Chester University E-mail: zjiang@wcupa. edu url: www. cs. wcupa. edu/~zjiang

Outline l Introduction to UML l Objects and Classes l Class Diagrams – Class Icon – Relationships – Constraints

Introduction to UML l What’s UML l Goals of UML l Overview

UML: Unified Modeling Language l The Unified Modeling Language (UML) is an industry-standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems l The UML definition was led by Grady Booch, Ivar Jacobson, and Jim Rumbaugh (all now at Rational Software)

l. UML simplifies the process of software design, making a "blueprint" for construction In Essence: a tool used through the analysis and design phases of system development for expressing the constructs and relationships of complex systems Target Usage: for building object-oriented and component-based systems

Goals of UML 1. Provide users with a ready-to-use, expressive visual modeling language so they can develop and exchange meaningful models 2. Provide extensibility and specialization mechanisms to extend the core concepts. 3. Be independent of particular programming languages and development processes. 4. Provide a formal basis for understanding the modeling language. 5. Encourage the growth of the Object-Oriented tools market. 6. Support higher-level development concepts such as collaborations, frameworks, patterns and components. 7. Integrate best practices.

l. Many free learning materials on the web – e. g. www. rational. com/uml l. Standard of UML www. cs. wcupa. edu/~zjiang/01 -09 -67. pdf l. Some recommended texts on UML: – The Unified Modeling Language User Guide, [G. Booch, J. Rumbaugh, I. Jacobson, 2000] – UML Explained, [Kendall Scott, 2001] – Applying UML and Patterns 2 nd Ed. , [Craig Larman, 2002] – UML Distilled 2 nd Ed. , [Martin Fowler with K. Scott, 2000] – UML and C++, [R. Lee & W. Tepfenhart, 2001]

UML Overview l UML is a language for visualizing, specifying, constructing and documenting the artifacts of a software system l The artifacts might include requirements, architecture, design, source code, project plans, tests, prototypes, releases l Six diagram types will be introduced: class, relationship, constraint, activity, sequence, statechart

Objects and Classes l What’s object – Identity – State – Behavior l l Sequence Diagram Statechart Diagram Messages and methods What’s class – – – – Objects and Classes Nature of a class Class Attributes Operation (Method) Interfaces and Implementation Corresponding C++ code

Objects and Classes l Fundamentals Programming of Object-Oriented

Objects l Conceptually, there are many ways to think of an object – something that can be seen or touched – a thing to which some action is directed – something that performs an action l The structure and behaviour of similar objects are defined in their common class l Objects have thee properties: identity , state, and behaviour

Object Property 1: Identity l Identity is that property of an object which distinguishes it from all other objects l Most programming languages use variable names to refer to objects l Keep in mind, however, that an object may not have a name; Similarly, an object might have multiple names (aliases) – For this reason, there is a subtle distinction made between the concepts of "name" and "identity"

Object Property 2: State l The state of an object encompasses all of the (usually static) properties of the object plus the current (usually dynamic) values of each of these properties

Object Property 3: Behaviour l Behaviour is how an object acts and reacts, in terms of its state changes and message passing l The state of an object represents the cumulative results of its behaviour l In object-oriented programming, a behaviour is invoked by sending a message to an object l If the receiver object does not have a method for that message, an error is reported

Sequence Diagrams l. A sequence diagram is an interaction diagram that focuses on the time ordering of messages l A vertical dashed line is used to represent the lifetime of an object (it’s the object’s lifeline) l A focus of control is a tall, thin rectangle that shows the period of time during which an object is performing an action

: Pilot : ATC request. Ldg. Clearance(r) : Radar check. Weather check. Runway. Clear(r) clearance

Sequence

Statechart Diagram l Captures dynamic behavior (event-oriented) l Purpose – Model object lifecycle – Model reactive objects (user interfaces, devices, etc. )

Example Objects l There are many physical objects we can examine right in this room – each person is an object – any chair is not an object – each light bulb is an object – Any book is not an object – this room itself is an object (full or not)

l See if the followings are objects or not: – – – – – l Desk Light Person Log The Earth Clock Machine Computer Saving account Answer: N, Y, Y, Y

Messages and Methods l. A object executes a method when it is sent a message l For example, we can ask/tell a dog to sit by sending him the message "sit" l In object-oriented programming, objects are sent messages asking/telling them to perform behaviours -- the object invokes the method corresponding to the message in order to execute the desired behaviour

Objects versus Classes l How would we describe the state, behaviour, and identity for each of these objects l We have looked at objects and we have seen that objects can be "classified" into classes l As programmers, we work with both classes and objects from those classes l For example, we might write a stack class and create multiple stack objects for use in our program

Classes and Objects l An object is called an "instance" of a class l The terms instance and object are interchangeable l Creating an object from a class is often called instantiation l For example, there are many person objects in this room -- each person is an instance of the person class

The Nature of a Class l. A class describes the common structure (attributes/state) and behaviour of its instances l For example, – 3. 14, 2. 71, and 5. 5 can be classified as Floats – the following shapes can be classified as Circles

l In a 2 D drawing package, circles have a radius, a line thickness, a line colour, and a fill colour l Each individual circle (instance) drawn by the user has its own value for each attribute l The programmer writes a Circle class and the program instantiates a Circle object every time the user draws a Circle a snowman made from 9 Circle instances

Class Attributes An attribute is a named property of a class that describes the range of values that instances of the property may hold. (Booch, 1999) l An attribute has a type that defines the type of its instances. l Only the object itself should be able to change the value of its attributes. l The values of the attributes define the state of the object l

Operation (Methods) l An operation is the implementation of a service that can be requested from any object of the class to affect behavior (Booch, 1999) l An operation can be: – Question (does not change the value of the object) – Command (may change the value of the object)

Interfaces An interface is a collection of operations that are used to specify a service of a class or a component (Booch, 1999) l An interface is a contract of related services and a set of conditions that must be true for the contract to be faithfully executed l Interfaces formalize polymorphism, they allow us to define polymorphism in a declarative way unrelated to implementation l

Interface and Implementation l The class interface is its external (public) view l The class implementation is its internal (private) view l It is convenient to think of the interface as describing "what the objects of this class can do" and the implementation as "how the objects of this class do it" l The implementation of a class consists of all the "behind the scenes" operations defined in the interface of the class

Review something Object action state 1 state 2 operations/methods attributes: {attribute 1, attribute 2} structure operation/method attribute 1 attribute 2 value

Light On Turn on/off Off operations/methods: Turn_on/off ( ) attributes: {True, False} structure Turn_on True False Turn_off value

C++ code class Light { public: void turn_on(); void turn_off(); Light(); ~Light(); private: bool status; }; // // Modifier Constructor Destructor

Class heading (class Light) & head file (light. h) l Operation implementation (light. cc) & library (light. o, light. lib) l Usage (message/event, interface and its implementation) & main (classroom. cc) l int main() { Light s 1[2]; //Class obj 1, obj 2; while (1){ Event event; event. receive_message(); //receive task for (int i = 0 ; i < 2; i ++){ //for all the objs // concerned, interface if (event. needs_turn_on()) s[i]. turn_on (); //interface implement } //end of one iteration } //end of while return 0; }

Class Diagram l Introduction l Class Icon l Relationships l Constraints

Introduction l The class diagram is fundamental to objectoriented programming l UML’s class diagrams capture the attributes and operations of each class as well the relationships that exist between classes

Class Icon l l l Class Icon Hiding Details Visibility Notation Attribute Specification Operation Specification

UML Class Icon l The UML class icon is a rectangle with three compartments: – class name – class attributes – class operations l Attributes are specified in the following form: – object: class name Circle radius: float center_x: int center_y: int area() display()

Hiding Detail l You can optionally leave out the attributes, operations, or both in a class icon: Circle area() display() Circle radius: float center_x: int center_y: int Circle

UML Member Visibility Notation l. UML has three visibility prefixes for members: + for public, # for protected, and – for private – e. g. Circle -radius: float #area() +display()

Full UML Attribute Specification l The full form of a UML attribute is as follows: [visibility] name [multiplicity] [: type] [= initial value] [{property}] – The property choices are changeable, add. Only, and frozen Student Info -id: string -has. Graduated: bool = false

l. The Full UML Operation Specification full form of a UML operation is as follows: [visibility] name [(parameter-list)] [: return-type] [{property}] – The property choices are sequential, concurrent, guarded, and is. Query l. The full form of a UML parameter is: [direction] name : type [= default-value] – The direction choices are in, out, and inout

UML Class Relationships l. A class relationship is a connection between two (or more) classes l The three most important class relationships are generalizations, associations, and aggregations l UML provides a graphical representation for each of the relationships using a different line type for each relationship

Class Relationships l Generalization l Association Class l Qualified Association l Ternary Association l Aggregation

Generalization A generalization is a relationship between a general thing (superclass) and a more specific kind of that thing (subclass) l In the UML, generalization requires that objects of the subclass may be used anywhere an object of the superclass appears l Person Student

Generalization Class Person { public: Person( long ); ~Person(); void show_id(); private: long ssn; }; // Constructor // Destructor // social security number Class Student : public Person { public: Student( long, long ); ~Student(); void show_info(); private: long sn; // student number };

Generalization Person: : Person (long number) { ssn=number; } Student: : Student (long snumer, long ssnumber): Person(ssnumber) { sn=snumber; } void Student: : show_info () { Person: : show_id(); cout << “; student number is “ << sn <<endl; } void Person: : show_id () { cout << “Social security number is “ << ssn <<endl; }

Generalization int main () { Person a(900010034); a. show_id(); Student b(123456789, 654321); b. show_info(); }

Generalization Class Person { public: Person( long ); ~Person(); void show_id(); protected: long ssn; }; // Constructor // Destructor // social security number Class Student : public Person { public: Student( long, long ); ~Student(); void show_info(); private: long sn; // student number };

Generalization void Student: : show_info () { cout << “Social security number is “ << ssn <<endl; cout << “; student number is “ << sn <<endl; }

Generalization Class Person { public: Person( long ); // Constructor ~Person(); // Destructor virtual void show_info()=0; protected: long ssn; // social security number }; Class Student : public Person { public: Student( long, long ); ~Student(); void show_info(); private: long sn; // student number };

Generalization void Student: : show_info () { cout << “Social security number is “ << ssn <<endl; cout << “; student number is “ << sn <<endl; }

Association l. An association is a structural relationship that specifies that objects of one thing are connected to objects of another Faculty Student

Association Class Student { // other declarations as before private: Faculty * teacher; friend Faculty: : add_new_student( Student *); friend Faculty: : remove_from_list ( Student *); public: Faculty * get_teacher () {return teacher; } }; Class Faculty : public Student //it’s not generalization { // other declarations as before private: Student ** students; public: void add_new_student ( Student *); void remove_from_list( Student *); Student ** get_students () {return students; } };

Association void Faculty: : add_new_student ( Student * s) { s->teacher = this; // add s to students; } void Faculty: : remove_from_list (Student * s) { s->teacher = 0; // remove s from students; }

Association l. Associations can be adorned with a name. Teaching Faculty Student

Association l. Associations Faculty can be adorned with the roles. teacher learner Student

Association l. Associations Faculty can be adorned with the multiplicity. 1 4. . * Student

Association Class (relation attributes) l Each object of association class is one instance of relationship (link) in an association. Faculty 1. . * 4. . * Course Student

Qualified Association l Qualified association relates two classes and a qualifier. l The qualifier is a special attribute that reduces the effective multiplicity of an association. Directory file name File

Ternary Association l A ternary association is a structural relationship that specifies that objects of one thing are connected to objects of other two’s. Project Language Developer

Aggregation l An aggregation is an association that represents whole/part relationship l The “whole” end of the association relationship is adorned with an open diamond shape (e. g. X is part of Y) l e. g. door: Door is part of car: Car X Y

Generalization, Aggregation, and Association l See if the following pairs of classes have generalization, aggregation or association l l l l l Faculty & student (as) Hospital & doctor (as) Door & Car (ag --<>) Member & Organization (ag --<>) People & student (ge <|-- ) Circle & point (ge --|>) Department & Faculty (as) Employee & Faculty (ge <|--) Item & Printer (ge <|--) Account & Checking account (ge <|-- )

Constraints l Constraints on Object l Constraints on Relations (Ordering) l General Constraints (Dependency)

Constraints on Object l. The constraints restricts the values that objects can be. l. Example: No employee’s salary can exceed the salary of the employee’s boss. {salary <=boss. salary} Employee Salary Employer Salary

Constraints on Relations (Ordering) l{Order} indicates that the elements of the “many” end of an association have an explicit order that must be preserved. {ordered} Paper 1 1. . * Author

General Constraints (Dependency) l A dependency is a using relationship that states that a change in specification of one thing may affect another thing that uses it (but not necessarily the reverse)

General Constraints (Dependency) l Dependencies are often used when one class uses another class as an argument of the operation Aerodrome check. RVR( r: Runway ) l Runway Dependencies are also often used to express general constraints. member-of Person {subset} chair-of Committee