GeneralizableElement

NamespaceModelElement

namevisibilityisSpecification

Classifier

isRoot

Constraint

Body

Coming up: Class Syntax

Basic Class Diagrams

CS/SWE 421

Introduction to Software Engineering

Dan Fleck(Slides adapted from Dr. Stephen Clyde with permission)

Tool Issue (Jan 28, 2010) Netbeans 6.8 is out and the old UML plugin is no longer

maintained or working in 6.8 Another option: Visual Paradigm Community Edition (

http://www.visual-paradigm.com/download/sdenb.jsp?edition=ce ) Install Netbeans 6.8 Install SDE 5.2 Community Edition Register for Community (free) license Start Netbeans Create a project (any type) Tools-> Start SDE CE-NB

Coming up: Class Names

Class Syntax A box divided into

compartments– Name– Attributes– Operations– Responsibilities (rarely

seen)– Used-defined

compartments (rarely seen)

Student

major: Stringgpa: Realstanding: String

add(Class Section)drop(Class Section)

-- The set of students known to the registration system

-- An exception occurs if gpa falls below 2.0

Coming up: Exercise – Class Identification

Class Names The name should be a noun or noun

phrase The name should be singular and

description of each object in the class The name should be meaningful from a

problem-domain perspective– “Student” is better than “Student Data” or

“S-record” or any other implementation driven name

Coming up: Attributes

Exercise – Class Identification

Identify meaningful classes in the Elevator System

Coming up: Attributes from an Analysis Perspective

Attributes Attributes represent characteristics or

properties of classes They are place holders or slots that hold

values The values they hold are other objects (or

primitive types)

Coming up: Attribute Syntax

Attributes from an Analysis Perspective An attribute relates an object to some other

object It has the same semantics as an association

joe: Student

name: String = “Joe Jones”

joe: Student Joe Jones : String

Is basically the same as ...

name

1

Coming up: Operations

Attribute Syntax

visibility: public “+”, protected “#”, or private “-”

name: capitalize first letter of each word that makes up the name, except for the first

multiplicity: number, range, or sequence of number or ranges.

type: build-in type or any user-defined class

initial-value: any constant and user-defined object

property-string: e.g, changeable, addOnly, frozen

[visibility] name [multiplicity] [:type] [=initial-value][{property-string}]

Coming up: Operation Syntax

Operations

Student

major: String

GPA: Real

standing: String

add(Class Section)

drop(Class Section)

Class Section

name: String

capacity: Integer

add(Student)

drop(Student)

checkPrerequisites(Students)

Prerequisite<

has

takes>

Course

Coming up: Type of Relationships in Class Diagrams

Operation Syntax

visibility: “+”, “#”, “-”

name: verb or verb phase, capitalize first letter of every word, except first

parameter-list: coma separated list of parameters

return-type: primitive type or user-defined type

property-string: isQuery, sequential, guarded, concurrent

[visibility] name [(parameter-list)] [:return-type] [{property-strong}]

Coming up: Associations

Type of Relationships in Class Diagrams

Relation

A consolidated snippet of the UML Meta-model

AssociationGeneralization Dependency

Aggregation

Binary Association N-ary Association

Coming up: Associations

Associations An association is a structural relationship

that specifies that objects of class may be connected to objects of another class

Associations typically represent “long-lived” relationships (– e.g. In a library system a Person always has

a name (association), but may infrequently have a book (dependency)

Coming up: Association Names

Associations

Student

Class Section

Course

Semester

Instructor

Department

takes>

is registered for>

teaches>

sponsors>

<w

orks

for is instance of>

is he

ld d

urin

g>

Coming up: Navigation

Association Names

Associations may be named– The names should communicate the

meaning of the links– The names are typically verb phases– The name should include an arrow

indicating the direction in which the name should be read

– The direction on the name does NOT change navigability!

Coming up: Navigation

Navigation The navigation of associations can be

– uni-directional– bi-directional– unspecified

Navigation is specified by the arrow, not the label

Class Section

Course

Instructor

Department

teaches>

sponsors>

<w

orks

for is instance of>

Coming up: Generalization

Navigation

The navigation of association without an arrowhead is assumed to be undefined

Navigation has less value when modeling from a conceptual perspective– Why?

Navigation is more important during specification and implementation perspectives– Why?

Coming up: Exercise – Simple Associations

Generalization Generalization is another kind of

relationship in UML In a Java implementation what is this?

StudentPerson Graduate Student

Coming up: Class Diagrams

Exercise – Simple Associations

From an analysis perspective:– Identify meaningful associations and

generalization/specializations among classes in the Elevator System

Coming up: Multiplicity Constraints

Class Diagrams

Class Diagrams describe– the types of objects in a system– their properties (attributes and operations)– relationships between objects

They can also include– Grouping concepts like packages– Constraints– Various kinds of annotations

Coming up: Questions

Multiplicity Constraints

Student

Class Section

Course

Semester

Instructor

Department

takes>

is registered for>

teaches>

sponsors>

<w

orks

for is instance of>

is he

ld d

urin

g>

1..*1

1..*

1..*11

1..*

0..8

0..*

0..61..3

Questions

From the previous diagram– How many classes can a student take?– Do you have to be registered in any classes

to be a student?– Do I need to teach this class to be an

Instructor? Do I need to teach ANY classes?

– Can a class have no students? Is that valid?

Coming up: Multiplicity Constraints

Coming up: Dependencies

Multiplicity Constraints

A multiplicity constraint can be– a single number– a “*”, meaning an arbitrarily large number or

simply “many”– a range, denoted by “min..max”– a sequence of single numbers and ranges

1..2,7,10-20

This is also called the cardinality constraintThis is also called the cardinality constraint

Coming up: Dependency Relationship

Dependencies

Relation

A consolidated snippet of the UML Meta-model

AssociationGeneralization Dependency

Aggregation

Binary Association N-ary Association

Coming up: Dependencies

Dependency Relationship It says that

one modeling component “uses” another.

If the later changes then, the former may have to change as well

Coming up: Aggregations (is part of)

Dependencies

Syntax:– a dashed link with an straight-line

arrowhead point to a component on which there is a dependency

Dependencies can be defined among: classes, notes, packages, and other types of components

Can dependencies go both ways? Any problems with having lots of

dependencies?

Coming up: Aggregation

Aggregations (is part of)

Relation

A consolidated snippet of the UML Meta-model

AssociationGeneralization Dependency

Aggregation

Binary Association N-ary Association

Coming up: Composition (very similar to aggregation)

Aggregation Aggregation: is a special kind of association

that means “part of” Aggregations should focus on single type of

composition (physical, organization, etc.)

1 1

*

4..*

1

1

1 1

1..3 1

0..9 1

Pizza Order

Slice

Crust

Sauce Serving

Cheese Serving

Topping Serving

Coming up: Lets look at BookstoreExample4.jpg

Composition (very similar to aggregation)

Think of composition as a stronger form of aggregation. Composition means something is a part of the whole, but cannot survive on it’s own.

BuildingRoom

Lets look at BookstoreExample4.jpg Does John McCain (who has 7 houses) have

a problem using this system? If Barack Obama decides to create a Federal

sales tax, how would we change the system?

Why is there a display method in Item, Book, MusicCD and Software?

An ItemOrder is part of how many Orders? Can you explain how a search works using

this diagram?Coming up: Class Exercise

Class Exercise

Lets create the WeGrow class diagram

Coming up: Safety System Example

Safety System Example A safety software system for housing areas:

– enables its owner to configure it during installation, – controls through its sensors the environmental areas against fire and burglary and – interacts with the owner through the keypad of the system control panel.

During installation, the system programming and configuration is carried out by using the numerical and functional keys of the control panel. Each sensor in the system is identified by a number and a type (fire or burglary). The system stores two passwords (each of them is up to six digits) used for the system activation/deactivation and a telephone number used for emergency calls when an alarm event arises. The system polls the fire sensors for M seconds, then disables them for other N seconds. After that, the system resumes the same cycle. The Ready indicator is lighting when the sensors are polled and is turned o when ffthe sensors are disabled. When a sensor indicates an event, the system launches an alarm signal. After K seconds, the system calls the security forces office and provides it with information about the event nature and location. In order to log in, the owner enters the password and presses Enter. If any of the six digits is wrong the password is ignored by the system and the sensors’s state doesn’t change. The owner can cancel the password with the Clear key. If a sensor is activated, the system is armed and the Armed indicator on the control panel is turn on. In the case of the sensor deactivation, the Armed indicator is turn o . Moreover, the ffsystem logs all events. Each logged event is characterized by its type and the date and time of its occurrence. The event list can be delivered by pressing the MEM key.

Coming up: Questions

Example specification from: http://www.emis.de/journals/ASUO/mathematics/pdf3/bogdan.ps

Coming up: More Questions

Questions What’s the difference between an attribute and an

association with another class? For example, should “grade” be an attribute or a link to another class called “Grade”?

When during the software engineering life cycle should you build classes diagrams?

Coming up: What’s important

More Questions

How do you know when a class diagram is complete?

How can you manage change control on all the class diagrams for project?

What do you do with class diagrams after a system has been built and delivered?

What’s important

Understading the 3 main parts of the class box

Generalization/Specialization Associations and multiplicity constraints Aggregation (and composition) understand

how to use them, but don’t worry about the differences between them – too subtle

Coming up: Bonus Slide!

Bonus Slide!

If you’re interested in Auto-generating UML, Netbeans has an option to do it.– Install the UML plugin– Right-click on a project– Choose “Reverse Engineer”– Go to the new UML project– Select a package and choose to generate a

new UML diagram This may not be true anymore with the new

plugin!

End of presentation