60-322 Object-Oriented Analysis and Design Feb 11, 2009.

60-322 Object-Oriented Analysis and Design

Feb 11, 2009

Feb 11, 2009 2

We were discussing Object Design. There are two kinds of object models: dynamic and static. What's important is knowing how to think and design in objects,

and apply object design best-practice patterns, which is a very different and much more valuable skill than

knowing UML notation.

The UML includes interaction diagrams to illustrate how objects interact via messages. They are used for dynamic object modeling.

There are two common types: – sequence and communication interaction diagrams.

Last lecture covered….

Feb 11, 2009 3

Diagram Frames in UML Sequence Diagram Basic Sequence Diagram Notation

To support conditional and looping constructs (among many other things), the UML uses frames.

Frames are regions or fragments of the diagrams; they have an operator or label (such as loop) and a guard(conditional clause).

enterItem(itemID, quantity)

: B

endSale

a UML loop frame, with a boolean guard expression description, total

makeNewSale

[ more items ]loop

: A

Feb 11, 2009 4


Feb 11, 2009 5


calculate

: Bar

yy

xx

[ color = red ]opt

: Foo

[ color = red ] calculate

: Bar

yy

xx

: Foo

Feb 11, 2009 6


: B: A

calculate

doX

: C

calculate

[ x < 10 ]alt

[ else ]

Feb 11, 2009 7


st = getSubtotal

lineItems[i] :SalesLineItem

t = getTotal

loop

: Sale

Feb 11, 2009 8

How to Relate Interaction Diagrams Basic Sequence Diagram Notation

interaction occurrence

note it covers a set of lifelines

note that the sd frame it relates to has the same lifelines: B and C

doA

: A : B : C

doB

sd AuthenticateUser

refAuthenticateUserauthenticate(id)

doX

doM1

: B : C

authenticate(id)

doM2

refDoFoo

sd DoFoo

doX

: B : C

doY

doZ

Feb 11, 2009 9


An interaction occurrence (also called an interaction use) is a reference to an interaction within another interaction.

It is useful, for example, when you want to simplify a diagram and factor out a portion into another diagram, or there is a reusable interaction occurrence.

UML tools take advantage of them, because of their usefulness in relating and linking diagrams.

Feb 11, 2009 10


They are created with two related frames:– a frame around an entire sequence diagram , labeled with the tag sd

and a name, such as AuthenticateUser.– a frame tagged ref, called a reference, that refers to another named

sequence diagram; it is the actual interaction occurrence.

Guideline: – Any sequence diagram can be surrounded with an sd frame, to name it. Frame

and name one when you want to refer to it using a ref frame

interaction occurrence

note it covers a set of lifelines

note that the sd frame it relates to has the same lifelines: B and C

doA

: A : B : C

doB

sd AuthenticateUser

refAuthenticateUserauthenticate(id)

doX

doM1

: B : C

authenticate(id)

doM2

refDoFoo

sd DoFoo

doX

: B : C

doY

doZ

Feb 11, 2009 11

Message to Classes to Invoke Static Methods Basic Sequence Diagram Notation

You can show class or static method calls by using a lifeline box label that indicates the receiving object is a class, or more precisely, an instance of a metaclass

Feb 11, 2009 12


Feb 11, 2009 13

Polymorphic Messages and Cases Basic Sequence Diagram Notation

Polymorphism is fundamental to OO design. How to show it in a sequence diagram?

One approach is to use multiple sequence diagrams - one that shows the polymorphic message to the abstract super class or interface object, and

then separate sequence diagrams detailing each polymorphic case, each starting with a found polymorphic message.

Feb 11, 2009 14


:Register

authorize

doX

:Payment {abstract}

polymorphic messageobject in role of abstract superclass

:DebitPayment

doA

authorize

:Foo

stop at this point – don’t show any further details for this message

doB

:CreditPayment

doX

authorize

:Bar

Payment {abstract}

authorize() {abstract}...

CreditPayment

authorize()...

DebitPayment

authorize()...

Payment is an abstract superclass, with concrete subclasses that implement the polymorphic authorize operation

separate diagrams for each polymorphic concrete case

Feb 11, 2009 15

Ch 15.5 Basic Communication Diagram Notation - Link

1: makePayment(cashTendered)2: foo

2.1: bar: Register :Sale

link line

A link is a connection path between two objects; it indicates some form of navigation and visibility between the objects is possible.

More formally, a link is an instance of an association.

For example, there is a link - or path of navigation - from a Register to a Sale, along which messages may flow, such as the makePayment message.

Feb 11, 2009 16

Message

Each message between objects is represented with a message expression and small arrow indicating the direction of the message.

Many messages may flow along this link. A sequence number is added to show the

sequential order of messages in the current thread of control.

1: msg22: msg33: msg4

3.1: msg5: Register :Sale

all messages flow on the same link

msg1Don't number the starting message. It's legal to do so, but simplifies the overall numbering if you don't.

Feb 11, 2009 17

Message to “self” or “this”

A message can be sent from an object to itself. This is illustrated by a link to itself, with messages

flowing along the link.

: Register

msg1

1: clear

Feb 11, 2009 18

Creation of Instance

The convention in the UML is to use a message named create for this purpose (some use new).

If another (less obvious) message name is used, the message may be annotated with a UML stereotype, like so: «create».

The create message may include parameters, indicating the passing of initial values. – This indicates, for example, a constructor call with parameters in Java. – Furthermore, the UML tagged value {new} may optionally be added to the lifeline box to highlight

the creation. Tagged values are a flexible extension mechanism in the UML to add semantically meaningful information to a UML element.

Feb 11, 2009 19

1: create(cashier)

: Register :Sale

create message , with optional initializing parameters . This will

normally be interpreted as a constructor call .

«create»

1: make(cashier ): Register :Sale

if an unobvious creation message name is used , the

message may be stereotyped for clarity

1: create(cashier )

: Register :Sale {new}

Three ways to show creation in a

communication diagram

The convention in the UML is to use a message named create for this purpose (some use new).

If another (less obvious) message name is used, the message may be annotated with a UML stereotype, like so: «create».

Feb 11, 2009 20

Message Numbering

: Amsg1 : B1: msg2

: C

1.1: msg3not numbered

legal numbering

The order of messages is illustrated with sequence numbers. The numbering scheme is:

– The first message is not numbered. Thus, msg1 is unnumbered.

– The order and nesting of subsequent messages is shown with a legal numbering scheme in which nested messages have a number appended to them. You denote nesting by prepending the incoming message number to the outgoing message number.

Feb 11, 2009 21

Message Numbering – A More Complex Case

: Amsg1 : B1: msg2

: C

1.1: msg3

2.1: msg5

2: msg4

: D

2.2: msg6

first second

fourth

sixth

fifth

third

Feb 11, 2009 22

Conditional Message

You show a conditional message by following a sequence number with a conditional clause in square brackets, similar to an iteration clause.

The message is only sent if the clause evaluates to true.

1 [ color = red ] : calculate: Foo : Bar

message1

conditional message, with test

Feb 11, 2009 23

Mutually Exclusive Conditional Paths

1a [test1] : msg2

: A : B

: C

1a.1: msg3

msg1

: D

1b [not test1] : msg4

1b.1: msg5

: E

2: msg6

unconditional after either msg2 or msg4 1a and 1b are mutually

exclusive conditional paths

Feb 11, 2009 24

Iteration or Looping

1 * [ i = 1..n ]: num = nextInt: SimulatorrunSimulation : Random

iteration is indicated with a * and an optional iteration clause following the sequence number

Feb 11, 2009 25

Iteration or Looping

1 * [i = 1..n]: st = getSubtotal: Salet = getTotal

This lifeline box represents one instance from a collection of many SalesLineItem objects.

lineItems[i] is the expression to select one element from the collection of many

SalesLineItems; the ‘i” value comes from the message clause.

lineItems[i]:SalesLineItem

this iteration and recurrence clause indicates we are looping across each element of the

lineItems collection.

1 *: st = getSubtotal: Salet = getTotal lineItems[i]:SalesLineItem

Less precise, but usually good enough to imply iteration across the collection members

Feb 11, 2009 26


You can show class or static method calls by using a lifeline box label that indicates the receiving object is a class, or more precisely, an instance of a metaclass

Feb 11, 2009 27

Messages to a Classes to Invoke Static (Class) Methods –Communication Diagram

1: locs = getAvailableLocales: Foo

«metaclass»Calendar

doX

message to class, or a static method call

Feb 11, 2009 28


:Register

authorize

doX

:Payment {abstract}

polymorphic messageobject in role of abstract superclass

:DebitPayment

doA

authorize

:Foo


doB

:CreditPayment

doX

authorize

:Bar

Payment {abstract}

authorize() {abstract}...

CreditPayment

authorize()...

DebitPayment

authorize()...

Payment is an abstract superclass, with concrete subclasses that implement the polymorphic authorize operation


Feb 11, 2009 29

Polymorphic Messages–Communication Diagram

:Register authorizedoX :Payment {abstract}

polymorphic message

object in role of abstract superclass

:DebitPayment

authorize

:Foo



doAdoB :CreditPayment

authorize

:BardoX

Feb 11, 2009 30

The UML includes class diagrams to illustrate classes, interfaces, and their associations.

They are used for static object modeling. – We've already introduced and used this UML diagram while domain

modeling, applying class diagrams in a conceptual perspective.

This chapter summarizes more of the notation, irrespective of the perspective (conceptual or software).

As with the prior interaction diagram chapter, this is a reference.

– Subsequent chapters focus on a more important question: What are key principles in OO design? Those chapters apply UML interaction and class diagrams to help explain and demonstrate object design.

Ch 16 UML Class Diagram

Feb 11, 2009 31

Ch 16 UML Class Diagram

java . awt :: Fontor

java . awt . Font

plain : Int = 0 { readOnly }bold : Int = 1 { readOnly } name : Stringstyle : Int = 0...

getFont ( name : String ) : FontgetName () : String

...

«interface»Runnable

run ()

- ellipsis “…” means there may be elements , but not shown- a blank compartment officially means “unknown” but as a

convention will be used to mean “no members”

SubclassFoo

...

run ()...

SuperclassFooor

SuperClassFoo { abstract }

- classOrStaticAttribute : Int+ publicAttribute : String- privateAttribute

assumedPrivateAttributeisInitializedAttribute : Bool = true

aCollection : VeggieBurger [ * ]attributeMayLegallyBeNull : String [ 0 .. 1 ]

finalConstantAttribute : Int = 5 { readOnly }/ derivedAttribute

+ classOrStaticMethod ()+ publicMethod ()

assumedPublicMethod ()- privateMethod ()# protectedMethod ()~ packageVisibleMethod ()

«constructor» SuperclassFoo ( Long )methodWithParms ( parm 1 : String , parm 2 : Float )

methodReturnsSomething () : VeggieBurgermethodThrowsException () { exception IOException }

abstractMethod ()abstractMethod 2 () { abstract } // alternate

finalMethod () { leaf } // no override in subclasssynchronizedMethod () { guarded }

3 common compartments

1 . classifier name

2 . attributes

3 . operations

interface implementation

andsubclassing

Fruit

...

...

PurchaseOrder

...

...

1

association with multiplicities

dependency

officially in UML , the top format is used to distinguish the package

name from the class name

unofficially , the second alternative is common

order

an interface shown with a

keyword

Much of the high-frequency class diagram notation can be summarized (and understood) in the figure below.

Most elements in the figure are optional (e.g., +/- visibility, parameters, compartments). Modelers draw, show or hide them depending on context and the needs of the reader or UML tool.

Feb 11, 2009 32

As we know, the same UML diagram can be used in multiple perspectives.

In a conceptual perspective the class diagram can be used to visualize a domain model.

For discussion, we also need a unique term to clarify when the class diagram is used in a software or design perspective.

A common modeling term for this purpose is design class diagram (DCD).

In the UP, the set of all DCDs form part of the Design Model. Other parts of the Design Model include UML interaction and package diagrams.

Definition: Design Class Diagram

Feb 11, 2009 33

A UML classifier is "a model element that describes behavioral and structure features".

Classifiers can also be specialized. They are a generalization of many of the elements of the UML, including classes, interfaces, use cases, and actors.

In class diagrams, the two most common classifiers are regular classes and interfaces.

Definition: Classifier

Feb 11, 2009 34

Attributes of a classifier (also called structural properties in the UML) are shown several ways:– attribute text notation, such as currentSale

: Sale.– association line notation– both together

Show UML Attributes: Attribute Text and Association Lines

Feb 11, 2009 35


Register

...

...

Sale

...

...

1

Register

currentSale : Sale

...

Sale

...

...

using the attribute text notation to indicate Register has a reference to one Sale instance

using the association notation to indicate Register has a reference to one Sale instance

OBSERVE: this style visually emphasizes the connection between these classes

currentSale

Register

currentSale : Sale

...

Sale

...

...

1thorough and unambiguous, but some people dislike the possible redundancy

currentSale

Feb 11, 2009 36

The full format of the attribute text notation is:visibility name : type multiplicity = default {property-string}

Also, the UML allows any other programming language syntax to be used for the attribute declaration.

visibility marks include + (public), - (private), and so forth.

Guideline: Attributes are usually assumed private if no visibility is given.


Feb 11, 2009 37

Notice in the previous figure that this attribute-as-association line has the following style:

– a navigability arrow pointing from the source (Register) to target (Sale) object, indicating a Register object has an attribute of one Sale

– a multiplicity at the target end, but not the source end

– a rolename (currentSale) only at the target end to show the attribute name

– no association name


Register

...

...

Sale

...

...

1

Register

currentSale : Sale

...

Sale

...

...

using the attribute text notation to indicate Register has a reference to one Sale instance

using the association notation to indicate Register has a reference to one Sale instance

OBSERVE: this style visually emphasizes the connection between these classes

currentSale

Register

currentSale : Sale

...

Sale

...

...

1thorough and unambiguous, but some people dislike the possible redundancy

currentSale

Feb 11, 2009 38

Guideline: When showing attributes-as-associations, follow this style in DCDs, which is suggested by the UML specification.

Guideline: On the other hand, when using class diagrams for a domain model do show association names but avoid navigation arrows, as a domain model is not a software perspective.


the association name, common when drawing a domain model, is often excluded (though still legal) when using class diagrams for a software perspective in a DCD

Register

id: Int

...

Sale

time: DateTime

...

1

currentSale

Register

id : Int

Sale

time : DateTime

Captures-current-sale1 1UP Domain Modelconceptual perspective

UP Design ModelDCD

software perspective

Feb 11, 2009 39

Guideline:

Use the attribute text notation for data type objects and the association line notation for others.

When to Use Attribute Text versus Association Lines for Attributes?

Register

id: Int

...

Sale

time: DateTime

...

1applying the guideline to show attributes as attribute text versus as association lines

Store

address: Addressphone: PhoneNumber

...

1

Register has THREE attributes:1. id2. currentSale3. location

currentSale

location

Feb 11, 2009 40

these different styles exist only in the UML surface notation; in code, they boil down to the same thing - the Register class will have three attributes.

For example, in Java:

public class Register {

private int id;

private Sale currentSale;

private Store location;

// …

}

When to Use Attribute Text versus Association Lines for Attributes?

Feb 11, 2009 41

The UML Notation for an Association End

notice that an association end can optionally also have a property string such as {ordered, List}

Sale

time: DateTime

...

SalesLineItem

...

...

1..*lineItems

{ordered, List}

Sale

time: DateTimelineItems : SalesLineItem [1..*] orlineItems : SalesLineItem [1..*] {ordered}

...

SalesLineItem

...

...

Two ways to show a collection attribute

Feb 11, 2009 42

The end of an association can have a navigability arrow.

It can also include an optional rolename (officially, an association end name) to indicate the attribute name.

The association end may also show a multiplicity value, such as '*' or '0..1'.

The rolename is used to indicate the attribute name


Feb 11, 2009 43

A property string such as {ordered} or {ordered, List} is possible for an association end.

{ordered} is a UML-defined keyword that implies the elements of the collection are ordered.

Another related keyword is {unique}, implying a set of unique elements.

The keyword {List} illustrates that the UML also supports user-defined keywords.

One may define {List} to mean the collection attribute lineItems will be implemented with an object implementing the List interface


Feb 11, 2009 44

Collection Attributes

notice that an association end can optionally also have a property string such as {ordered, List}

Sale

time: DateTime

...

SalesLineItem

...

...

1..*lineItems

{ordered, List}

Sale

time: DateTimelineItems : SalesLineItem [1..*] orlineItems : SalesLineItem [1..*] {ordered}

...

SalesLineItem

...

...

Two ways to show a collection attribute

60-322 Object-Oriented Analysis and Design Feb 11, 2009.

Documents

Transcript of 60-322 Object-Oriented Analysis and Design Feb 11, 2009.