An introduction to UML - IDATDDC32/lectures/TDDC32-6.1-UML.pdf · An introduction to UML Calin...

An introduction to UMLCalin Curescu

An introduction to UML

Calin Curescu

Figures taken from Borland tutorial

http://bdn.borland.com/article/0,1410,31863,00.html

27 pagesTDDC32 lecture 6, 2006


2 of 27TDDC32 lecture 6, 2006

What is a Process?

• A Process is a series of definable, repeatable, and measurable tasks leading to a useful result.

• Analysis: User needs are gathered and converted into software requirements. – What is to be done to meet user needs?

• Design: Determines organisation of various modules in the software system – How to meet the user needs?

• Construction: Coding is the main activity in this phase • Testing:

– Unit testing, integration testing, and system testing. • Implementation• Maintenance (some say 80% of costs)



Unified process (RUP)

• Good practices of modern software development

• Uses UML :)

• Iterative• Incremental• Architecture-Centric• Use Case driven



What is UML

• Software development– A Process– A modeling language

• The Unified Modeling Language (UML) is called a modeling language, not a method. The modeling language is the notation that methods use to express designs.

• Models in software help us to visualize, specify, construct and document the artifacts of a software intensive system.

• UML provide various perspectives– User, Structural, Behavioral, Implementation, Environment– Using diagrams – why?

1 bitmap = 1 megaword



Diagrams

• Use case diagrams • Class diagrams • Object diagrams • Sequence diagrams • Collaboration diagrams• Statechart diagrams • Activity diagrams • Component diagrams • Deployment diagrams



Use case diagrams

• What a system does from the standpoint of an external observer

• Emphasis is on what a system does rather than how

• A scenario is an example of what happens when someone interacts with the system

• Use case is a summary of scenarios for a single task or goal

• Actors are simply roles that people or objects play– Initiates the events



A use case example

• Use case “Make appointment”– Represented by ovals

• Actor: “Patient”– Represented by stick figures

• Connection: “communication association”– Lines that link actors to use cases

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 diagrams

• Collection of actors, use cases, and their communications• Can also show:

– System boundaries• Separates actors from system

– Generalizations• One use case is a special case of another

– Includes• Several subtask can be identified out of a larger use case

– Extensions• One use case is a variation of another• Do not confuse with generalization (like expands)• Extension point



Use case diagram example



Class diagram

• Static overview of a system• UML class notation

– Class name• Italics: abstract classes

– Attributes– Operations

• Relationships– Association

• Knows about the other end– Aggregation

• One class belongs to a collection• Diamond on the container side

– Generalization• One class is other’s superclass• Triangle points to superclass

• Relationships• Connected links• An end may have a role

name• Navigability

• Arrow - direction of association or query (“has”)

• No arrow – bidirectional• Multiplicity

• number of possible instances of the class associated with a single instance of the other end



Class diagram exampleMultiplicities Meaning

0..1 zero or one instance. The notation n . . m indicates n to m instances.

0..* or * no limit on the number of instances (including none)

1 exactly one instance

1..* at least one instance



Composition

• Stronger than aggregation• The part can belong to only one whole

– Cannot exist without whole• Filled diamond at the whole end



Visibility and scope



Dependencies and constraints

• Dependency– A change in a class may force a change in the other– Drawn as dotted lines– Observe the arrowQ: Are dependencies good?

• Constraint– A condition that every implementation of the system must

satisfy– Constraints are written in curly braces { }



Example dep. & const.



Interfaces

• Implementation (or realization) relationship with a class

• Dashed line, triangle points to interface

• Set of operation signatures

• Interfaces and their method names are written in italics



Object diagrams

• Show more complicated relationships

• Instance names are underlined

• Class names are preceded by : (colon)



Sequence diagram

• Sort of interaction diagram, dynamic• Details how operations are carried out

– What messages and when• Timeline towards bottom of page• Life line

– Shows object exists– Dotted line– Can contain activation bars

• Triggered by received messages• Messages

– Directed horizontal lines• Can be a self call• Iterations denoted by *• Conditions denoted with [ ]

– Usually implemented by method invocation but not always



Sequence diagram example



Asynchronous messages

Symbol Meaning

simple message which may be synchronous or asynchronous

simple message return (optional)

a synchronous message

an asynchronous message



Collaboration diagrams• Also an interaction diagram• Focus on object roles instead of

message sending times• Links represent messages• Sequence number

– Can be used to show order in a message sequence

– Top level message numbered 1– Messages at same level have same

prefix but suffixes grow according to the order when they occur



Statechart diagrams

• Possible states of the system– Rounded rectangles– Observe special initial and final states

• Transitions– From a state to another, represented by arrows– Triggering conditions or events written besides arrows– Guards are denoted in [ ]

• Actions– Can be attached to transitions or states

• A validating state does not need external event as trigger– Denoted by a preceding /



Statechart diagrams Example



Activity diagram

• Fancy flowchart, related to statechart– Focuses on flows (not on the states)– Has a sense of sequentiality (order in time)

• Swimlanes determine which object is responsible for what• A single transition comes out from each activity

– May branch or merge – represented by a hollow diamond– Guard expressions on any transitions coming from a branch

• Denoted in [ ]• Synchronization bars

– Denote beginning (fork) and end (join) of parallel activities– Denoted by solid bars



Activity diagram example



Component and deployment diagrams

• A deployment diagram shows the physical configuration of hardware and software

• A component is a code module– Denoted as a rectangle with two bars on upper left

• A node represents physical hardware– Each component belongs to a node



Deployment diagram example



Reading

• Mandatory– http://pigseye.kennesaw.edu/~dbraun/csis4650/A&D/UML_tut

orial/index.htm– http://bdn.borland.com/article/0,1410,31863,00.html

• Others

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