Unified Modeling Language Object Oriented Analysis and Design

Tom Meyer, Iowa State
Meyer@iastate.edu
SCT/Pixel Online Workshop
18-19 June, 2001
UML and OOAD
Unified Modeling Language
Object Oriented Analysis and Design

Meyer@iastate.edu
18-19 June, 2001
UML Origins
A product of the “design wars” of the 1980’s
Grady 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

Meyer@iastate.edu
18-19 June, 2001
What 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.”

Meyer@iastate.edu
18-19 June, 2001
What 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 UML
Rational Rose
Rhapsody

Meyer@iastate.edu
18-19 June, 2001
UML 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
dateReceived
isPrepaid
number : String
prince : Money
dispatch()
close()
Customer
name
address
creditRating():String
* 1
Personal
Customer
creditCard#
Corporate
Customer
contactName
creditRating
creditLimit
remind()
billForMonth(Integer)
Order Line
quantity : Integer
price : Money
isSatisfied : Boolean
Employee
*
0..1
Product
* 1
*
1
{creditRating()==
"poor"}
sales rep
line
items
Multiplicity: mandatory
Association
Role
Name
Attributes
Operations
Generalization
(inheritance)
Class
Multiplicity: optional
Multiplicity: many-valued

Meyer@iastate.edu
18-19 June, 2001
UML 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 Order Entry
window
an Order an Order Line a Stock Item
a Reorder
Item
a Delivery
Item
prepare()
* prepare()
hasStock:=
check()
hasStock:=
remove() needsReorder:=
needsToReorder()
[needsReorder]
new
[hasStock] new
Object
Message
Iteration
Condition
Self-Call
Return
Creation
Deletion

Meyer@iastate.edu
18-19 June, 2001
UML 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/check
item
Dispatching
do/initiate
delivery
Waiting Delivered
[Not all items checked]
/get next item
/get first item
[All items checked &&
all items available]
Delivered
Item Received
[some items not in stock]
start
state
self-transition
transition
activity
I
t
e
m
R
e
c
e
i
v
e
d
[
a
l
l
i
t
e
m
s
a
v
a
i
l
a
b
l
e
]

Meyer@iastate.edu
18-19 June, 2001
OOAD
• 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).

Meyer@iastate.edu
18-19 June, 2001
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.

Meyer@iastate.edu
18-19 June, 2001
Example 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.

Meyer@iastate.edu
18-19 June, 2001
VME Crate (2)
The OO way:
Void initCrate(crateNumber)
{
// interate over modules
Module.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()

Meyer@iastate.edu
18-19 June, 2001
VME Crate (3)
• The module-specific details are encapsulated inside the
object.
• The various init routines are polymorphic as seen from the
outside world.

Meyer@iastate.edu
18-19 June, 2001
Example 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.

Meyer@iastate.edu
18-19 June, 2001
References
ISBN: 020165783X ISBN: 0132038374

Unified Modeling Language Object Oriented Analysis and Design

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