UML Diagrams By Muhammad Aamir Salem Unified Modeling

UML Diagrams By: Muhammad Aamir Salem

Unified Modeling Language n n Unified Modeling Language (UML) is a standardized general-purpose modeling language in the field of software engineering. The standard is managed, and was created by, the Object Management Group. UML includes a set of graphic notation techniques to create visual models of software-intensive systems.

Using Use Case Diagrams n n Use case diagrams are used to visualize, specify, construct, and document the (intended) behavior of the system, during requirements capture and analysis. Provide a way for developers, domain experts and end-users to Communicate. Serve as basis for testing. Use case diagrams contain use cases, actors, and their relationships. 3

Use Case n name Use cases specify desired behavior. A use case is a description of a set of sequences of actions, including variants, a system performs to yield an observable result of value to an actor. Each sequence represent an interaction of actors with the system. מידע מערכות ניתוח 4

Specifying the Behavior of a Use Case n n n Describing the flow of events within the use case. Can be done in natural language, formal language or pseudo-code. Includes: how and when the use case starts and ends; when the use case interacts with actors and what objects are exchanged; the basic flow and alternative flows of the behavior. 5

Actors n n name An actor represents a set of roles that users of use case play when interacting with these use cases. Actors can be human or automated systems. Actors are entities which require help from the system to perform their task or are needed to execute the system’s functions. Actors are not part of the system. 6

Use Cases and Actors n n From the perspective of a given actor, a use case does something that is of value to the actor, such as calculate a result or change the state of an object. The Actors define the environments in which the system lives 7

Example of Use Case Diagram registration student updating grades faculty output generating 8

Relationships between Use Cases 1. Generalization - use cases that are specialized versions of other use cases. 2. Include - use cases that are included as parts of other use cases. Enable to factor common behavior. 3. Extend - use cases that extend the behavior of other core use cases. Enable to factor variants. 9

1. Generalization n n The child use case inherits the parent behavior and meaning of the parent use case. child The child may add to or override the behavior of its parent. 10

More about Generalization registration non-graduate registration 11

2. Include base n n <<include>> included The base use case explicitly incorporates the behavior of another use case at a location specified in the base. The included use case never stands alone. It only occurs as a part of some larger base that includes it. 12

More about Include n Enables to avoid describing the same flow of events several times by putting the common behavior in a use case of its own. updating grades <<include>> output generating <<include>> verifying student id 13

3. Extend base n n <<extend>> extending The base use case implicitly incorporates the behavior of another use case at certain points called extension points. The base use case may stand alone, but under certain conditions its behavior may be extended by the behavior of another use case. 14

More about Extend n Enables to model optional behavior or branching under conditions. Exam copy request <<extend>> Examgrade appeal 15

Relationships between Actors n Generalization. student graduate student non-graduate student 16

Relationships between Use Cases and Actors n Actors may be connected to use cases by associations, indicating that the actor and the use case communicate with one another using messages. updating grades faculty 17

Example cellular network user place conference call place phone call <<extend>> receive phone call <<extend>> additional receive call use scheduler Cellular Telephone 18

A More Complicate Example 19

Use Case Description Each use case may include all or part of the following: § § § § Title or Reference Name - meaningful name of the UC Author/Date - the author and creation date Modification/Date - last modification and its date Purpose - specifies the goal to be achieved Overview - short description of the processes Cross References - requirements references Actors - agents participating Pre Conditions - must be true to allow execution Post Conditions - will be set when completes normally Normal flow of events - regular flow of activities Alternative flow of events - other flow of activities Exceptional flow of events - unusual situations Implementation issues - foreseen implementation problems 20

Example- Money Withdraw n n n Use Case: Withdraw Money Author: ZB Date: 1 -OCT-2004 Purpose: To withdraw some cash from user’s bank account Overview: The use case starts when the customer inserts his credit card into the system. The system requests the user PIN. The system validates the PIN. If the validation succeeded, the customer can choose the withdraw operation else alternative 1 – validation failure is executed. The customer enters the amount of cash to withdraw. The system checks the amount of cash in the user account, its credit limit. If the withdraw amount in the range between the current amount + credit limit the system dispense the cash and prints a withdraw receipt, else alternative 2 – amount exceeded is executed. Cross References: R 1. 1, R 1. 2, R 7 21

Example- Money Withdraw (cont. ) n n Actors: Customer Pre Condition: n n The ATM must be in a state ready to accept transactions The ATM must have at least some cash on hand that it can dispense The ATM must have enough paper to print a receipt for at least one transaction Post Condition: n n n The current amount of cash in the user account is the amount before the withdraw minus the withdraw amount A receipt was printed on the withdraw amount The withdraw transaction was audit in the System log file 22

Example- Money Withdraw (cont. ) § Typical Course of events: Actor Actions System Actions 1. Begins when a Customer arrives at ATM 2. Customer inserts a Credit card into ATM 3. System verifies the customer ID and status 5. Customer chooses “Withdraw” operation 4. System asks for an operation type 7. Customer enters the cash amount 6. System asks for the withdraw amount 8. System checks if withdraw amount is legal 9. System dispenses the cash 10. System deduces the withdraw amount from account 11. System prints a receipt 13. Customer takes the cash and the receipt 12. System ejects the cash card 23

Example- Money Withdraw (cont. ) n Alternative flow of events: n n Step 3: Customer authorization failed. Display an error message, cancel the transaction and eject the card. Step 8: Customer has insufficient funds in its account. Display an error message, and go to step 6. Step 8: Customer exceeds its legal amount. Display an error message, and go to step 6. Exceptional flow of events: n Power failure in the process of the transaction before step 9, cancel the transaction and eject the 24 card

Example- Money Withdraw (cont. ) § One method to identify use cases is actor-based: - Identify the actors related to a system or organization. - For each actor, identify the processes they initiate or participate in. A second method to identify use cases is event-based: - Identify the external events that a system must respond to. § - Relate the events to actors and use cases. § The following questions may be used to help identify the use cases for a system: - - What are tasks of each actor ? Will any actor create, store, change, remove, or read information in the system ? What use cases will create, store, change, remove, or read this information ? Will any actor need to inform the system about sudden, external changes ? Does any actor need to be informed about certain occurrences in the system ? Can all functional requirements be performed by the use cases ? 25

Moving on n n The “things” that “live” inside the system are responsible for carrying out the behavior the actors on the outside expect the system to provide. To implement a use case, we create a society of classes that work together to carry out the behavior of the use case. 26

Class Diagrams n n The main building block in object oriented modeling They are used both for general conceptual modeling of the systematics of the application, and for detailed modeling translating the models into programming code The classes in a diagram represent both the main objects and/or interactions in the application and the objects to be programmed In the diagram these classes are represented with boxes which contain three parts

Class Diagrams n A class with three sections. n n n The upper part holds the name of the class The middle part contains the attributes of the class The bottom part gives the methods or operations the class can take or undertake

Class Diagrams n n In the system design of a system, a number of classes are identified and grouped together in a class diagram which helps to determine the static relations between those objects With detailed modeling, the classes of the conceptual design are often split in a number of subclasses In order to further describe the behavior of systems, these diagrams can be complemented by state diagram or UML state machine Also instead of class diagrams, Object role modeling can be used if you just want to model the classes and their relationships

The class icon n Defines n n n The class icon has n n Persistent system state System behavior Name Attributes Operations It’s a rectangle divided into three compartments.

Steps followed n n n Draw class symbol in the editor and name it List the class attributes List the class operations/methods Make the links and associations Give notations

Structural Modeling: Core Elements Reference: OMG tutorial on UML by Cris Kobryn

Structural Modeling: Core Elements (cont’d) ¹ An extension mechanism useful for specifying structural elements. Reference: OMG tutorial on UML by Cris Kobryn

Structural Modeling: Core Relationships Reference: OMG tutorial on UML by Cris Kobryn

Structural Modeling: Core Relationships (cont’d) Reference: OMG tutorial on UML by Cris Kobryn

Interfaces: Longhand Notation Fig. 3 -29, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Associations n n n An Association represents a family of links Binary associations (with two ends) are normally represented as a line, with each end connected to a class box Higher order associations can be drawn with more than two ends; in such cases, the ends are connected to a central diamond Fig. 3 -40, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Associations n n An association can be named, and the ends of an association can be adorned with role names, ownership indicators, multiplicity, visibility, and other properties There are five different types of association; bi-directional and uni-directional associations are the most common ones Fig. 3 -40, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Aggregations n n n Aggregation is a variant of the "has a" or association relationship; aggregation is more specific than association It is an association that represents a part-whole or part-of relationship. As a type of association, an aggregation can be named and have the same adornments that an association can However, an aggregation may not involve more than two classes

Aggregations (Weak type) n n n Aggregation can occur when a class is a collection or container of other classes, but where the contained classes do not have a strong life cycle dependency on the container—essentially, if the container is destroyed, its contents are not In UML, it is graphically represented as a hollow diamond shape on the containing class end of the tree of lines that connect contained class(es) to the containing class Example: Football team players n If one gone, other may survive

Composition (Strong type) n n n Composition is a stronger variant of the "owns a" or association relationship; composition is more specific than aggregation It is represented with a solid diamond shape Has a strong life cycle dependency between instances of the container class and instances of the contained class(es): If the container is destroyed, normally every instance that it contains is destroyed as well Note that a part can (where allowed) be removed from a composite before the composite is deleted, and thus not be deleted as part of the composite The UML graphical representation of a composition relationship is a filled diamond shape on the containing class end of the tree of lines that connect contained class(es) to the containing class Example : House with rooms Fig. 3 -45, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Generalization n Indicates that one of the two related classes (the subtype) is considered to be a specialized form of the other (the super type) and supertype is considered as 'Generalization' of subtype In practice, this means that any instance of the subtype is also an instance of the supertype An exemplary tree of generalizations of this form is found in binomial nomenclature: human beings are a subtype of simian, which are a subtype of mammal, and so on. The relationship is most easily understood by the phrase 'A is a B' (a human is a mammal, a mammal is an animal). Fig. 3 -47, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Generalization n n The UML graphical representation of a Generalization is a hollow triangle shape on the supertype end of the line (or tree of lines) that connects it to one or more subtypes. The generalization relationship is also known as the inheritance or "is a" relationship. n n The supertype in the generalization relationship is also known as the "parent", superclass, base class, or base type. The subtype in the specialization relationship is also known as the "child", subclass, derived type, inheriting class, or inheriting type. Fig. 3 -47, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Generalization n n Note that this relationship bears no resemblance to the biological parent/child relationship: the use of these terms is extremely common, but can be misleading Generalization-Specialization relationship n n n A is a type of B E. g. "an oak is a type of tree", "an automobile is a type of vehicle" Generalization can only be shown on class diagrams and on Use case diagrams. Fig. 3 -47, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

Dependencies n n Dependency is a weaker form of relationship which indicates that one class depends on another because it uses it at some point of time It exists if a class is a parameter variable or local variable of a method of another class Fig. 3 -50, UML Notation Guide Reference: OMG tutorial on UML by Cris Kobryn

UML Class Diagram Examples Reference: www. smartdraw. com

UML sequence diagrams n sequence diagram: an "interaction diagram" that models a single scenario executing in the system n n relation of UML diagrams to other exercises: n 70 perhaps 2 nd most used UML diagram (behind class diagram) n CRC cards -> class diagram use cases -> sequence diagrams

Key parts of a sequence diag. n participant: an object or entity that acts in the sequence diagram n n n message: communication between participant objects the axes in a sequence diagram: n 71 sequence diagram starts with an unattached "found message" arrow n horizontal: which object/participant is acting vertical: time (down -> forward in time)

Sequence diag. from use case 72

Representing objects n squares with object type, optionally preceded by object name and colon n n 73 write object's name if it clarifies the diagram object's "life line" represented by dashed vert. line

Messages between objects n message (method call) indicated by horizontal arrow to other object n n n 74 write message name and arguments above arrow dashed arrow back indicates return different arrowheads for normal / concurrent (asynchronous) methods

Lifetime of objects n creation: arrow with 'new' written above it n n notice that an object created after the start of the scenario appears lower than the others deletion: an X at bottom of object's lifeline n Java doesn't explicitly delete objects; they fall out of scope and are garbagecollected 75

Indicating method calls n activation: thick box over object's life line; drawn when object's method is on the stack n n either that object is running its code, or it is on the stack waiting for another object's method to finish nest to indicate recursion Activation Nesting 76

Indicating selection and loops n frame: box around part of a sequence diagram to indicate selection or loop n n n if -> (opt) [condition] if/else -> (alt) [condition], separated by horiz. dashed line loop -> (loop) [condition or items to loop over] opt [balance <>0] alt [balance < 100. 00] [balance>= 100. 00] loop 77 [balance < 0]

linking sequence diagrams n if one sequence diagram is too large or refers to another diagram, indicate it with either: n n n 78 an unfinished arrow and comment a "ref" frame that names the other diagram when would this occur in our system?

Example sequence diagram 79

(De)centralized system control n What can you say about the control flow of each of the following systems? n n 80 centralized? distributed?

Flawed sequence diagram 1 n 81 What's wrong with this sequence diagram? (Look at the UML syntax and the viability of the scenario. )

Flawed sequence diagram 2 n 82 What's wrong with this sequence diagram?

Flawed sequence diagram 3 n What's wrong with this sequence diagram? : Computer : Print. Server print(file) [if printer free] print(file) [else] enqueue(file) 83 : Printer : Queue

Why not just code it? Sequence diagrams can be somewhat close to the code level. So why not just code up that algorithm rather than a good sequence diagram is still a bit above the level of the drawing it as a sequence diagram? real code (not EVERY line of code is drawn on diagram) n n n sequence diagrams are language-agnostic (can be implemented in many different languages non-coders can do sequence diagrams easier to do sequence diagrams as a team can see many objects/classes at a time on same page (visual bandwidth) 84

Sequence diagram exercise 1 n 85 Let's do a sequence diagram for the following casual use case, Start New Poker Round : The scenario begins when the player chooses to start a new round in the UI. The UI asks whether any new players want to join the round; if so, the new players are added using the UI. All players' hands are emptied into the deck, which is then shuffled. The player left of the dealer supplies an ante bet of the proper amount. Next each player is dealt a hand of two cards from the deck in a round-robin fashion; one card to each player, then the second card. If the player left of the dealer doesn't

Sequence diagram exercise 2 n 86 Let's do a sequence diagram for the following casual use case, Add Calendar Appointment : The scenario begins when the user chooses to add a new appointment in the UI. The UI notices which part of the calendar is active and pops up an Add Appointment window for that date and time. The user enters the necessary information about the appointment's name, location, start and end times. The UI will prevent the user from entering an appointment that has invalid information, such as an empty name or negative duration. The calendar records the new appointment in the user's list of appointments. Any reminder selected by the user is added to the list of reminders. If the user already has an appointment at that time, the user is shown a warning message and asked to choose an available time or replace the previous