Tom Meyer, Iowa State [email protected] SCT/Pixel Online Workshop 18-19 June, 2001 UML and OOAD Unified Modeling Language Object Oriented Analysis and

Tom Meyer, Iowa [email protected]

SCT/Pixel Online Workshop18-19 June, 2001

UML and OOADUML and OOAD

Unified Modeling Language

Object Oriented Analysis and Design



UML OriginsUML Origins

A product of the “design wars” of the 1980’sGrady Booch, James Rumbaugh, and others had competing styles.

`94: Rumbaugh leaves GE to join Booch at Rational Software“Method wars over. We won.” Others feared achieving

standardization the Microsoft way.

’95: Rational releases UML 0.8; Ivars Jacobson (use cases) joins Rational“The Three Amigos”

’96: Object Management Group sets up task force on methods’97: Rational proposed UML 1.0 to OMG. After arm

twisting and merging, UML 1.1 emerges’99: After several years of revisions and drafts, UML 1.3 is

released



What UML isWhat UML is

• A way to express a software design, mostly through graphical tools

• Is important for communication, does not specify the process used to reach a design. That process is far more more nebulous

• Compare it to using circuit schematics and timing diagrams for documenting hardware designs

• Capture the important details, “the art is knowing what to leave out.”



What UML Can Do for UsWhat UML Can Do for Us

• Lets us make out mistakes on paper, before we write and debug the code

• Lets us communicate our ideas better

• Lets us tap into a wealth of existing designs (patterns) that lets us draw on others’ experience

• Lets us use existing tools designed around UMLRational Rose

Rhapsody



UML Tools: Class DiagramUML Tools: Class Diagram

•Captures the packaging of the solution into software objects.

•Elaborates the relationships betweeen objects, allowing dependencies to be controlled.

•In an OO language, leads directly to coded objects.

•A good basis for discussion and documentation.

•But, it only shows the static structure.

•Like a circuit diagram in electronics, it shows connectivity but not the dynamics of signals or messages.

Order

dateReceivedisPrepaidnum ber : S tringprince : Money

dispatch()close()

Custom er

nam eaddress

creditRating():S tring

* 1

PersonalCustom er

creditCard#

CorporateCustom er

contactNam ecreditRatingcreditLim it

rem ind()billForMonth(Integer)

Order Line

quantity : Integerprice : MoneyisSatisfied : Boolean

Em ployee

*

0..1

Product* 1

*

1

{creditRating()=="poor"}

sales rep

lineitem s

Multiplic ity: m andatory

Association

RoleNam e

Attributes

Operations

Generalization(inheritance)

Class

Multiplic ity: optional

Multiplic ity: m any-valued



UML Tools: Sequence DiagramUML Tools: Sequence Diagram

• Time runs downward

• Shows how objects interact

• Gives the sequence of interactions, but not the precise timing

• Roughly analogous to timing diagrams in electronics

• Have already been extremely useful in developing the DSP communication with the ROD hardware

an O rder Entryw indow

an O rder an O rder L ine a S tock Item

a R eorderItem

a D eliveryItem

prepare ()

* p repare ()

hasS tock :=check()

hasS tock :=rem ove() needsR eorde r:=

needsToR eorde r()

[needsR eorde r]new

[hasS tock ] new

O bject

M essage

IterationC ondition

Self-C all

R eturn

C reation

D eletion



UML Tools: State DiagramUML Tools: State Diagram

• Not much different from usage in many other areas

• Describes an object that changes state under specified transition activities and does specified activities in that state

• Another tool for describing dynamic behavior

Checking

do/checkitem

Dispatching

do/in itia tede livery

W aiting Delivered

[N ot a ll item s checked]/get next item

/get firs t item

[A ll item s checked &&all item s availab le ]

D elivered

Item R eceived[som e item s not in s tock ]

start

sta tese lf-transition

transition

activity



OOADOOAD

• Going to Object Oriented software is not just changing the syntax of the language. It is a new way of organizing software.

• An object is an instantiation of a class. Just as i can be an instantiation of type integer, x an instantiation of type float and “A” and instantiation of type char, an object myObj can be an instantiation of a (user-defined) class myClass.

• An object has a state (specified by values of attributes) and behavior (given by functions, or methods).



OOAD (2)OOAD (2)

• The idea is to keep as many of the details of the objects functionality inside the object and present only a well-defined interface to the outside world.

• Open to extending the behavior or the object, but closed to exposing changes inside the object to the outside world.

• Try to keep one piece of software from depending on changes to another piece.



Example 1: VME CrateExample 1: VME Crate

A VME crate has three modules in it: ADC, TDC, CPU.We need a routine that initializes the entire crate.

The old way:

Void initCrate(int crateNumber){ initADC(); initTDC(); initCPU();}

There are smarter ways (e.g. case statements), but there is no way to avoid the need for initCrate to call separate init routines for each type of module.



VME Crate (2)VME Crate (2)The OO way:

Void initCrate(crateNumber){// interate over modulesModule.init();}

The routine initCrate no longer needs to know what kind of module it is talking to. We could even add a new type of module and it wouldn’t care.

vmeModule

init()

adcModule

init()

tdcModule

init()

cpuModule

init()

vmeCrate

initCrate()



VME Crate (3)VME Crate (3)

• The module-specific details are encapsulated inside the object.

• The various init routines are polymorphic as seen from the outside world.



Example 2: Database AccessExample 2: Database Access

myDatabase

addRecord()

simpleTextDb

addRecord()

bigFancyOoDb

dbUser

storeInfo()

addRecord()

As long as the methods of dbUser refer to the interfaces of myDataBase, they will not care whether we use a simple ASCII text file or a messy object oriented database. We can go from one to the other without changing dbUser.



ReferencesReferences

ISBN: 020165783X ISBN: 0132038374

Documents

Tom Meyer, Iowa State [email protected] SCT/Pixel Online Workshop 18-19 June, 2001 UML and OOAD Unified Modeling Language Object Oriented Analysis and