UML Diagram @ Software engineering discussion

UML Diagrams
by Hnin Thiri Chaw (9PhD-3)
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• UML stand for “Unified Modeling Language”.
• There are nine kind of diagram in UML
1. Use case diagrams
2. Class diagrams
3. Object diagrams
4. Sequence diagrams
5. Collaboration diagrams
6. Statechart diagrams
7. Activity diagrams
8. Component diagrams
9. Deployment diagrams

• The communication among everyone involved in creating and deploying the software is critical in
complicated System.
• The software blueprint language for analysts, designers, and programmers alike. It isnow part of
the software trade.
• The UML gives everyone from business analyst to designer to programmer a common
vocabulary to talk about software design.
• The UML is applicable to object-oriented problem solving for the construction of a model.
• Models consist of objects.
Class
• Classes are the "blueprints" for objects.
• A class wraps attributes (data) and behaviors (methods or functions) into a single distinct
entity. Objects are instances ofclasses.

• Use case diagrams describe what a system does from the standpoint of an external observer.
• The emphasis is on what a system does rather than how a system does.
• Use case diagrams are closely connected to scenarios.
• A scenario is an example of what happens when someone interacts with the system. Here is a
scenario for a medical clinic.
Scenario
• "A patient calls the clinic to make an appointment for a yearly checkup. The receptionist finds the
nearest empty time slot in the appointment book and schedules the appointment for that time slot.“
Use Case
• A use case is a summary of scenarios for a single task or goal.
• An actor is who or what initiates the events involved in that task.
• Actors are simply roles that people or objects play.

Figure: Make Appointment use case for the medical clinic.
•The actor is a Patient.
• The connection between actor and use case is a communication association(or communication
for short).
Use Case Notation
•Actors are stick figures.
•Use cases are ovals.
•Communications are lines that link actors to use cases.

Figure: Make Appointment use case for the medical clinic with four actors and four use cases.
• A use case diagram is a collection of actors, use cases, and their communications.
• A single use case can have multiple actors.
• Use case diagrams are helpful in three areas.
– determining features (requirements). New use cases often generate new requirements as
the system is analyzed and the design takes shape.
– communicating with clients. Their notational simplicity makes use case diagrams a good
way for developers to communicate with clients.
– generating test cases. The collection of scenarios for a use case may suggest a suite of
test cases for those scenarios.

Figure: A customer order from a retail catalog
The central class is the Order.
Associated with it are the Customer making the purchase and the Payment. A Payment is one of three kinds:
Cash, Check, or Credit.
The order contains OrderDetails (line items), each with its associated Item.

• A Class diagram gives an overview of a system by showing its classes and the relationships
among them.
• Class diagrams are static -- they display what interacts but not what happens when they do
interact.
UML Class Notation
• UML class notation is a rectangle divided into three parts: class name, attributes, and
operations.
• Names of abstract classes, such as Payment, are in italics.
• Relationships between classes are the connecting links.
• A navigability arrow on an association shows which direction the association can be traversed
or queried.
• The arrow also lets you know who "owns" the association's implementation; in this case,
Order Detail has an Item.
• Associations with no navigability arrows are bi-directional.

• UML Class Notation
• The multiplicity of an association end is the number of possible instances of the class
associated with a single instance of the other end.
• Multiplicities are single numbers or ranges of numbers.
• In our example, there can be only one Customer for each Order, but a Customer can have any
number of Orders.
• This table gives the most common multiplicities.
Multiplicities Meaning
• 0..1 =>zero or one instance.
• 0..* or * => no limit on the number of instances (including none).
• 1 =>exactly one instance
• 1..* => at least one instance
• Every class diagram has classes, associations, and multiplicities. Navigability and roles are
optional items placed in a diagram to provide clarity.

Class Relationship
• Our class diagram has three kinds of relationships.
• Association -- a relationship between instances of the two classes.
• There is an association between two classes if an instance of one class must know about the
other in order to perform its work.
• In a diagram, an association is a link connecting two classes.
• Aggregation -- an association in which one class belongs to a collection.
• An aggregation has a diamond end pointing to the part containing the whole.
• In our diagram, Order has a collection of Order Details .(‘Has’)
• Generalization -- an inheritance link indicating one class is a superclass of the other.
• A generalization has a triangle pointing to the superclass.
• Payment is a superclass of Cash, Check, and Credit(‘Is’).
• An association has two ends.
• An end may have a role name to clarify the nature of the association.
• For example, an OrderDetail is a line item of each Order.

• To simplify complex class diagrams, classes are grouped into packages.
• A package is a collection of logically related UML elements.
Package Notation
• Packages appear as rectangles with small tabs at the top.
• The package name is on the tab or inside the rectangle.
• The dotted arrows are dependencies.
• One package depends on another if changes in the other could possibly force changes in the
first.
Figure: Package Diagram of the Banking Business Model

Figure: Object Diagram of the Department
of University containing many subdepartment
Object
•Objects that interact by sending each other messages. Think of an object as "alive.“
• Objects have => (1) things they know (attributes)
=> (2)the things they can do (behaviors or operations).
=> (3)the values of an object's attributes determine its state(attribute’s value).
•Object diagrams show instances instead of classes.
•They are useful for explaining small pieces with complicated relationships,
•especially recursive relationships.
Object Notation
Each rectangle in the object diagram corresponds to a single instance.
Instance names are underlined in UML diagrams.
Class or instance names may be omitted from object diagrams as long as
the diagram meaning is still clear.

•Class and object diagrams are static model views.
•Interaction diagrams are dynamic. They describe how objects collaborate.
•A sequence diagram is an interaction diagram that details how operations are carried
out -- what messages are sent and when. Sequence diagrams are organized according to
time.
•The objects involved in the operation are listed from left to right according to when they take
part in the message sequence.

Figure: Sequence Diagram of the Making Hotel Reservation
•The object initiating the sequence of messages is a Reservation window.
•The Reservation window sends a makeReservation() message to a HotelChain.
•The HotelChain then sends a makeReservation() message to a Hotel. If the Hotel has
available rooms, then it makes a Reservation and a Confirmation.
Sequence Notation
•Each vertical dotted line is a lifeline, representing the time that an object exists.
• Each arrow is a message call. An arrow goes from the sender to the top of the activation bar
of the message on the receiver's lifeline.
•The activation bar represents the duration of execution of the message.
•In our diagram, the Hotel issues a self call to determine if a room is available.
•If so, then the Hotel creates a Reservation and a Confirmation.
• The asterisk on the self call means iteration (to make sure there is available room for each day
of the stay in the hotel).
• The expression in square brackets, [ ], is a condition.
•The diagram has a clarifying note, which is text inside a dog-eared rectangle.
•Notes can be put into any kind of UML diagram.

Figure: Collaboration Diagram of the Making Hotel Reservation
Collaboration diagrams
• Collaboration diagrams are also interaction diagrams.
• They convey the same information as sequence diagrams, but they focus on object roles
instead of the times that messages are sent.
Difference between Sequence and Collaboration Diagram
• In a sequence diagram, object roles are the vertices and messages are the connecting links.
The object-role rectangles are labeled with either class or object names (or both). Class
names are preceded by colons ( : ).
• Each message in a collaboration diagram has a sequence number. The top-level message is
numbered 1. Messages at the same level (sent during the same call) have the same decimal
prefix but suffixes of 1, 2, etc. according to when they occur.

• Objects have behaviors and state.
• The state of an object depends on its current activity or condition.
• A statechart diagram shows the possible states of the object and the transitions that cause
a change in state.
State Diagram Notation
• States are rounded rectangles.
• Transitions are arrows from one state to another. Events or conditions that trigger transitions
are written beside the arrows. Our diagram has two self-transition, one on Getting SSN and
another on Getting PIN.
• The initial state (black circle) is a dummy to start the action.
• Final states are also dummy states that terminate the action.
• The action that occurs as a result of an event or condition is expressed in the form /action.
• While in its Validating state, the object does not wait for an outside event to trigger a transition.
Instead, it performs an activity.
• The result of that activity determines its subsequent state.

Figure: State Diagram of the Login Part of Online Banking System
• Our example diagram models the login part of an online banking system. Logging in consists
of entering a valid social security number(SSN) and personal id number(PIN),
thensubmitting the information for validation.
• Logging in can be factored into four non-overlapping states: Getting SSN, Getting PIN,
Validating, and Rejecting. From each state comes a complete set of transitions that
determine the subsequent state.

Figure: Activity Diagram Withdrawing Money from ATM
For our example, we used the following process.
"Withdraw money from a bank account through an ATM."
The three involved classes (people, etc.) of the activity are Customer, ATM, and Bank.

• An activity diagram is essentially a fancy flowchart.
• Activity diagrams and state chart diagrams are related.
Difference Between State Diagram and Activity Diagram
• While a state diagram focuses attention on an object.
• Activity diagram focuses on the flow of activities involved in a single process.
• The activity diagram shows the how those activities depend on one another.
Activity Diagram Notation
• The activities are rounded rectangles.
• The process begins at the black start circle at the top and ends at the concentric white/black
stop circles at the bottom.
• Activity diagrams can be divided into object swim lanes that determine which object is
responsible for which activity.
• A single transition comes out of each activity, connecting it to the next activity.
• A transition may branch into two or more mutually exclusive transitions.
• Guard expressions (inside [ ]) label the transitions coming out of a branch.
• A branch and its subsequent merge marking the end of the branch appear in the diagram as
hollow diamonds.
• A transition may fork into two or more parallel activities. The fork and the subsequent join of
the threads coming out of the fork appear in the diagram as solid bars.

Deployment Diagram
• Deployment diagrams show the physical configurations of software andhardware.
• The deployment diagram shows the relationships among software and hardware
components involved in real estate transactions.
• The physical hardware is made up of nodes.
Component Diagram
• A component is a code module. Component diagrams are physical analogs of class
diagram.
• Each component belongs on a node.
• Components are shown as rectangles with two tabs at the upper left.

UML Diagram @ Software engineering discussion

UML Diagram @ Software engineering discussion

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UML Diagram @ Software engineering discussion