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The object-oriented approach to requirements
The Unified Modeling Language and the Object Management Group
Object-Oriented Requirements
The Class Diagram
The System Activities:An Object-Oriented Use Case/Scenario View
Object Interactions: Collaboration and Sequence Diagrams
Object Behavior: States, State transition, and Statechart Diagrams
Management information system 7_ 1 Huang Hong
教学/考核要点
UML and OMG
Object-Oriented Requirements
System Activities
Class diagram
Use case and use case diagram
Actor，Scenario，use case
<Includes> relation between use cases
comparison between use case diagram and DFD
use case diagram development*
Object Interactions
Message
Sequence diagram
Symbols used in sequence diagram
sequence diagram comprehension*
sequence diagram development*
Collaboration diagram
Comparison of sequence diagram and collaboration diagram
Object Behavior:
States, State transition, and Statechart Diagram notation
Concurrent behavior
Statechart Diagram comprehension and development
Management information system 7_ 2 Huang Hong
Northwoods kayaks: identifying the methods
within the objects
From this Flash movie, what can we learn about the activities a
analyst must do during a system analysis using OO approach.
Can you tell some types of the models used in OO analysis.
Words:get the hang of (of sth.)熟悉某物的用法, 掌握做某事的窍
门, 理解某事, 摸清概况, 鉴赏
Management information system 7_ 3 Huang Hong
Overview
From the object-oriented viewpoint, the world consists of objects.
Any given business function is supported by a set of objects that
work together, or collaborate, to carry out the function. To do
object-oriented analysis, we first define the set of objects that will
make up the system. Then we describe how those objects work together.
There are two parts to this description. First we must understand
and describe the interactions or communication among the various
objects. These interactions take the form of messages between
objects. Second, we must describe the internal processing that goes
on within each object to respond to messages from other objects,
and to initiate messages to other objects.
Management information system 7_ 4 Huang Hong
The Unified Modeling Language and the
Object Management Group
UML(Unified Modeling Language) is an object-oriented modeling
notation[表示法]. It is a successor to the modeling techniques
found in Grady Booch’s Object Technology, James Rumbaugh’s
Object Modeling Technique(OMT), Ivar Jacobson’s Object
Oriented Software Engineering, and several other methods.
Preliminary version was presented in 1995.
OMG(Object Management Group, established in 1989) is a
consortium[协会] of over 800 software vendors, developers and
organizations that have combined theirs efforts to develop and
propagate uniformity[一致] in object-oriented systems. OMG’s
mission is to promote the theory and practice of object technology
for the development of distributed computing systems. The goal is
to provide a common architectural framework for object-oriented
applications based on widely available interface specifications.
UML have been submitted to OMG for consideration as a widely
accepted standard for OO modeling.
Management information system 7_ 5 Huang Hong
Object-Oriented Requirements
Five separate but interrelated, object-oriented models or diagrams
are used to define the system requirements. In some situations,
only three or four diagrams may be required to specify the
requirements accurately.
1. The class diagram
2. The use case diagram
3. The collaboration diagram
4. The sequence diagram
5. The statechart diagram
OO Requirements = Event Table + Class Diagram +Use Case
Diagrams + Interaction Diagrams(collaboration and/or sequence
diagrams) + Statechart Diagrams
Management information system 7_ 6 Huang Hong
Object-Oriented Requirements(cont.)
Use case diagram[用例图/使用实例图]
A diagram to show the various user roles and how those roles use the system. It is a
way to document the functions that a system must support. Sometimes a single,
comprehensive use case diagram is used to describe the entire system. At other
times, a set of smaller use case diagrams make up the use case model.
Collaboration diagram[合作图]
A diagram showing the objects that collaborate together to carry out a use case.
Objects collaborate with each other by sending messages. Generally many
collaboration diagrams are needed in a system’s requirements specification.
Message: the communication between objects within a use case
Sequence diagram[顺序图]
A diagram showing the sequence of messages between objects during a use case. It
contains the same information in a collaboration diagram, but emphasizes the
sequence of the message rather than the collaborating objects.
Interaction diagram[交互图]
Both the collaboration diagrams and the sequence diagrams are referred to as
interaction diagrams
Statechart diagram[状态图]
A diagram describe the states, states transition, and behavior of an object.
Management information system 7_ 7 Huang Hong
Requirements models for the traditional approach
and the object-oriented approach
object-oriented approach Events and traditional approach
Event table
Things
Use case Class Entity-relationship Context
diagrams Diagram diagram diagram
DFD
scenarios
fragments
Sequence Statechart
Detail DFDs Diagram 0
diagrams diagrams
Other OO Other
models definitions
Management information system 7_ 8 Huang Hong
The class diagram
We often divide the description of a system into two categories:
structural information and behavior information. Structural
information means the component parts of the system. Class
diagram provides the definition of the system components.
Class diagram provide the structure for the database, and the
structure of the computer program.
Class diagram will also include user-interface classes which is
called implementation classes.
Management information system 7_ 9 Huang Hong
The System Activities:An Object-Oriented Use Case/Scenario
View
Use Case and Actors
Use case[用例]
A single use or function performed by the system for those who use
the system. It is an activity the system carried out in response to an
event.
Actor [执行者]
A role played by a user of the system. A user can play several roles in
a system. An actor is always outside of the automation boundary of
the system.
Connecting line to
show which actors A use case
participate in which
Stick use cases
figure called a actor
and representing a role
Create new
order
Order clerk
System automation
boundary
Management information system 7_ 10 Huang Hong
Scenarios[场景、情节]
What is a scenario
A scenario is a particular sequence of activities within a use case; a use case may
have several different scenarios.
An example of scenario for use case “create new order”
Flow of activities for customer creates telephone order
Main flow: The customer call RMO and talk to an order clerk. The order
clerk verifies the customer information. If this is a first-time customer, a
new customer record is created. The customer requests the first item for
an order, this triggers the creation of a new order. The clerk verifies that
the item is in stock and adds the requested quantity to the order. The
customer then requests each item, and the clerk verifies it and adds it to
the order. Finally, the customer provides payment information, and the
clerk verifies it . The order is marked as ready, and the scenario ends.
Exception conditions: If an item is not in stock, then the customer can choose
not to order it or to put it on the order as a backorder item. If the
customer credit is no good, then the order is put on hold until a check is
received and cleared.
Flow of activities for customer creates Web order
…
Management information system 7_ 11 Huang Hong
The Use Case Diagram
What is a use case diagram?
A use case diagram is a graphical model that summarizes the information
about the actors and use cases.
What is the purpose of a use case diagram?
It is used as a functional description of the entire system
How to develop use case diagram
To do use case analysis we look at the system as a whole and try to
identify all of the major uses of the system.
Use cases normally derive from[得自] the business events identified in
the event table.
Management information system 7_ 12 Huang Hong
The Use Case Diagram(continue)
How to organize use cases in use case diagram
Use cases are normally organized in two ways:
Organizing the use cases by subsystem
Organizing the use cases By actor
All use cases involving customers
look up item
availability
Order entry subsystem
create new order
<<uses>>
Look up item <<uses>>
availability
<<uses>> <<uses>> update order
<<uses>>
<<uses>> <<uses>> <<uses>>
look up order
create new order status
<<uses>>
<<uses>> <<uses>>
customer order clerk <<uses>>
<<uses>>
customer
create order return
update order
provide catalog
info
update customer
account
Management information system 7_ 13 Huang Hong
The Use Case Diagram(continue)
“Include” relationship between use cases
What is a “include” relationship?
One use case to use the services of another use case.
An example of “include” relationship
use case create new order includes use case validate customer account.
use case update order also includes use case validate customer account .
In programming jargon[行话], use case such as validate customer account is
referred to as common subroutine.
Create new order
<<includes>
> <<includes>
look up item >
availability
<<includes> validate customer
> account
Customer Order clerk
<<includes>
>
Update order
Management information system 7_ 14 Huang Hong
Use Case Diagram Vs Data Flow Diagram
Similarity
Like context diagram, a use case diagram helps define the scope of the
system.
The individual use cases identify individual functions just like DFD
fragment
Differences
Automation boundary is defined from the beginning of the use case
diagram development. An actor must be the one who actually interacts
with the system. But in the development of a DFD, the automation
boundary often is not defined until the entire process has been detailed, an
external agent is always the original source or destination of the
information and may not necessarily be the one interacting with the
system.
Use case diagram does not indicate data flows.
Management information system 7_ 15 Huang Hong
Development of a use case diagram
Two possible starting points:
From event table
Identify all actors who use the system as specific roles
Once the actors and use cases have been identified, the next step is
to develop a flow of activities as the starting point for identifying
the various scenarios. As the different flows of activities are
developed, any common internal use cases can be identified
and separated into different use cases.
Management information system 7_ 16 Huang Hong
Object Interactions:
collaboration and sequence diagrams
What’s the purpose of Interaction diagram?
To describe the flow of information and interactions between objects.
Interaction diagram is a low level diagram of the use case diagram
use case diagram does not show the use case is performed by what objects and
what information is passed to each other between these objects, but interaction
diagram does.
Two types of interaction diagram:
Collaboration diagram
Sequence diagram
What’s similarities and differences between collaboration diagram and
sequence diagram?
Similarity:
contain the same information
Difference:
Collaboration diagram: focus more the objects that interact together to support
a use case. Top-down preferred analyst tend to draw collaboration diagram
first to get an overview of the objects that collaborate to carry out the use case.
Sequence diagram: focus more on the details of the messages. Bottom-up
preferred analyst frequently develop sequence diagram and never even draw a
collaboration diagram.
Sequence diagram is more complex and is used more frequently in industry.
Management information system 7_ 17 Huang Hong
The relationship between use case, class and
sequence diagrams
Class diagram Shipment
Use case diagram
Order
Create
new
Order clerk order Customer
Sequence diagram for create new order
Create order
:order :customer
Verify customer
Order clerk
Management information system 7_ 18 Huang Hong
A sequence diagram for the telephone-order scenario
of the “create new order” use case
:product item :inventory item
customer clerk
[NewCustomer]
CreateCustomer
(Customer Information) :customer
PhoneCall
[ExistingCustomer]
Status:=CheckStatus
(CustomerName, PhoneNo)
*RequestItem
(Catalog No,Qty) [FirstItem]CreateOrder
:order
AddToOrder(ProductID, Description, Qty)
Price:=CheckPrice(ProductID)
Quantity:=CheckQuantity
(ProductID , Description, Qty)
[QOH>Qty]CreateItem(itemID, Qty) :order item
AdditemConfirmation( )
FinishedOrdering OrderComplete(Credit Card Number) *ReadyToShip( )
Management information system 7_ 19 Huang Hong
Steps to develop a sequence diagram
Identify all the objects and actors that are involved in the scenario.
Use only actors who have been identified in the use case diagram. Use only objects
from classes that are identified in the class diagram. If objects or actors are needed
that have not been previously identified, then update those other diagrams.
Based on the flow of activities, identify eachmessage that will be required to carry
out the scenario. Identify both the source object or actor for the message and the
destination object or actor.
Identify source object
Identify the object that need the service
Identify the object that has access to the required input parameters
In a one-to-many association relationship from the class diagram, the one side
object usually send messages to the objects on the many side.
Next determine whether each message is always sent or whether it is sent only under
certain conditions.
Sequence the messages correctly and attach them to the appropriate lifeline of the
actors and objects.
Add the formal syntax on the message to describe conditions, message names,
and passed parameters
If desired, add the response message and communications to make the sequence diagram
complete.
Management information system 7_ 20 Huang Hong
A sequence diagram for the telephone-order scenario
of the “create new order” use case
:product item :inventory item
customer clerk
[NewCustomer]
CreateCustomer
(Customer Information) :customer
PhoneCall
[ExistingCustomer]
Status:=CheckStatus
(CustomerName, PhoneNo)
*RequestItem
(Catalog No,Qty) [FirstItem]CreateOrder
:order
AddToOrder(ProductID, Description, Qty)
Price:=CheckPrice(ProductID)
Quantity:=CheckQuantity
(ProductID , Description, Qty)
[QOH>Qty]CreateItem(itemID, Qty) :order item
AdditemConfirmation( )
FinishedOrdering OrderComplete(Credit Card Number) *ReadyToShip( )
Management information system 7_ 21 Huang Hong
Iteration in Object-Oriented Approach
Updating may required
The use case diagram and flow of events(activities) are used to build the
sequence diagram. The detail of the sequence diagram require the use of
class diagram. As you build the sequence diagram, you may discover that
the use cases, the flow of events, or the class diagram are incomplete
and may require updating.
One of the strengths of object-oriented development is that this
interconnectedness helps to ensure that the final system is complete,
comprehensive, and correct.
Management information system 7_ 22 Huang Hong
Collaboration Diagrams
Collaboration diagram is used to get a quick overview of the objects that collaborate
to support a given scenario.
A collaboration diagram uses the same symbols for actors, objects, and messages
found in sequence diagram, but the lifeline symbol is not used, and a new symbol,
the link symbol is used.
Message syntax in collaboration diagram:
[true/false condition]sequence number：return-value:=message-name(parameter-list)
An actor An object which receives a
who sends the initial message and sends other messages
message
1:FirstMessage( ) 2:SecondMessage( )
object1 object2
4:FinalResponse( ) 3:ReturnMessage( )
A link between symbols A message arrow
that send or receive messages and descriptive name
Management information system 7_ 23 Huang Hong
Collaboration Diagram Example
1:Itemquery( )
catalog
Customer 5:ItemAvailabilityInfo( )
4:Productinfo( ) 2:Productiteminquiry( )
3:InventoryInfo:=
InventoryIteminquiry( )
Product item Inventory item
Collaboration diagram for look up item availability
Management information system 7_ 24 Huang Hong
Statechart Diagram
What’s the purpose of a statechart diagram?
Statechart diagram is used to describe the internal working or
behavior of a object.
Who needs a statechart diagram
Each class in the class diagram of a system should have an unique
statechart diagram.
What’s the bases to build statechart diagrm
Statechart diagram is built based on information from the class diagram
and the sequence diagram.
Management information system 7_ 25 Huang Hong
Terms and Symbols used in Statechart Diagram
State
A state for an object is a condition during its life when it satisfies some
criteria, perform some action, or waits for an event.
Action
An activity performed by an object in a particular state.
Actions
State name that must be
performed during
the period the state
idle working is active
Load part
Mill part
Unload part
concentric circles with the
inside circle darkened denotes the final
A darkened circle state. This state indicate the exit from the
denotes an initial state and The state statechart, frequently indicating the
simply indicate the entry point to removal of the object from the system
transition
a statechart
Management information system 7_ 26 Huang Hong
Statechart diagram(cont.)
Transition
A component of a statechart that signifies[表示] the movement from one state to
the next. A transition is represented by an arrow and a label to describe the
components of the transition.
Message event(transition name) Guard condition
The trigger for a transition A true/false test to
consisting of a message that has see whether a
Origin the properties of an event transition can be taken. Destination
state state
Off OnButtonPushed [Bin not empty AND Safety cover closed]/ On
Status:=self-test( ); ControlPanel.UpdateState(status)
Action expression
The statement on a
transition to describe the
action to be performed
Management information system 7_ 27 Huang Hong
Statechart diagram(cont.)
Internal transition
A transition within a state that does not remove the object from the state
Three important internal transitions are used to define when action statements are
executed within a state.
Entry / action expression :activated at the moment that the object enters the state
Do / action expression :executes while the object is within the state
Exit / action expression :activated just before the object leaves the state
Idle Working
Entry/Load part
Do/Mill part
Exit/Unload part
Management information system 7_ 28 Huang Hong
Statechart diagram(cont.)
Messages, Transitions, and Actions
Usually, transition names take the form of formal syntax which corresponds to the
syntax of a message name:
Transition-name(paramters,…)
e.g. CreateItem(itemID,Qty)
Message sending and dot notation
Objects not only receive messages but send messages. Messages are normally sent
as part of an action statement which in turn are part of transitions or states.
To send a message, we normally use the syntax called dot notation.
ObjectName .MessageName(paramters,…)
Object name
or class name to which The milling machine铣床sent a message named
the message will be Updatestatus() to a object called ControlPanel,with a
directed parameter called status
Off OnButtonPushed [Bin not empty AND Safety cover closed]/ On
Status:=self-test( ); ControlPanel.UpdateState(status)
A part of a statechart of a milling machine object
Management information system 7_ 29 Huang Hong
relationship among OO models
Class diagram Shipment
Use case diagram
Order
Create
new
Order clerk order Customer
Sequence diagram for create new order
Create order :order :customer
Verify customer
Order clerk
Items being Ready to
entered ship
Statechart diagram for order class
Relationship among OO models
Management information system 7_ 30 Huang Hong
Relationship between class, statechart and
sequence diagrams
Customer Order item
Order class Product class
class class
Create new
× × × ×
order
Create new
×
customer
Check item
×
availability
The columns identified all classes in the system, each row is for
one sequence diagram, the ×s in the cells show which classes are
involved in which sequence diagrams. A statechart for a class is based on
the entire column for that class. Every cell with an × in it will provide
information about the messages to and from the class and will impact the
development of the statechart.
Management information system 7_ 31 Huang Hong
Statechart diagrams(sample)
CreateItem Waiting ShipItem
Exists ReadyToShip( ) (ItemID,Qty) Shipped
(ItemID,Qty) to be
shipped
Statechart diagram for order item object
An order item is an passive object with a very simple life cycle.
It comes into existence when an item is added to the order. While the
order is being completed, it is in a “do nothing” state
Once the order is completed, order item object moves to a state of
“waiting to be shipped”
Once the items have been shipped, the order item changes to a state of
“shipped”
Management information system 7_ 32 Huang Hong
Completion transition: A transition
Statechart diagrams(sample) with no trigger event so that it is taken
when the origin state completes its
action
Accepting items Verifying payment
CreateOrder(order information)/ Build
order information; associate with OrderComplete Do/ calculate total;
customer (CreditCard# ) Verify Credit
[Credit no good]
Decision
AddToOrder(Product ID,Description,Qty)/ pseudostate
ProductItem.CheckPrice();
InventoryItem.CheckQOH(); [CreditOK]
CreateOrderItem( )
PullNextItem( ) [Item Available] PullNextItem( ) [Item Not Available]
/Mark line /Mark line
“shipped” “Backorder”
Ready for fulfillment Pulling items for OrderShiped( )/ send shipped
shipment notice to customer
Entry/ For Each
OrderItem.ReadyToShip( );
CheckCleared( ) or CreditCleared( )
Closed
DeleteOrder( )
Statechart diagram for order object
Management information system 7_ 33 Huang Hong
How to develop statechart diagram
To develop the statechart diagram of an object
Identify all incoming message events across all sequence diagrams
involving the object.
Identify all output messages events across all sequence diagrams
involving the object
Brainstorms the possible states that might exist for the object.
The incoming message events help to identify transitions
Transitions are always connected to states
Insert appropriate intermediate state
Management information system 7_ 34 Huang Hong
Concurrent behavior of objects
Path
A valid sequence of transitions and status through a statechart
Concurrent behavior
An object can do multiple things in parallel, so within a statechart, there can
be more than one active state at a time.
An active path, particularly when multiple paths can be active concurrently, is
called a thread.
There are two types of notation to denote concurrent behavior in
statechart diagram
Composite state
Synchronization pseudostate
Management information system 7_ 35 Huang Hong
Composite state and Synchronization pseudostate
Composite state(复合状态)
A high level state with multiple compartments, each compartment
contains a thread (has other states nested in it).
State
State State
State State
Synchronization pseudostate（同步伪状态）
Use solid vertical bar to split paths into multiple threads and merge
multiple threads into a single thread.
State
State
Management information system 7_ 36 Huang Hong
An RMO customer statechart diagram with concurrent threads
PlaceOrder( )
Outstanding
Inactive order
PlaceOrder( )
AfterNoOrder(1 year)
未执行订单
Active
StartNewYear/ Zero annual purchases
Regular Special
Do/ accumulate annual Do/ accumulate
purchases [annual purchases > 1000] lifetime purchases
Do/ accumulate
lifetime purchases
PlaceOrder( )
Has Has
outstanding no
order [Outstanding order]
orders
ShipOrder( )
[No outstanding order]
Management information system 7_ 37 Huang Hong
An RMO customer statechart diagram
with Synchronization pseudostates
StartNewYear/ Zero annual purchases Special
Do/ accumulate
lifetime purchases
Regular
Do/ accumulate annual
purchases [annual purchases > 1000]
Do/ accumulate
lifetime purchases
PlaceOrder( ) Inactive
AfterNoOrder(1 year)
Has PlaceOrder( ) Has
outstanding no
order [Outstanding order]
orders
[No outstanding order]
ShipOrder( )
PlaceOrder( )
Management information system 7_ 38 Huang Hong
Statechart development
Statechart is difficult for new analyst to develop, the primary problem is
identifying the right states for the object. Another difficulty is to identify
and handle composite states with nested threads. It may be helpful to
pretend you are the object itself.
Developing statechart need more iteration.
Steps in developing state charts
Review the class diagram and select the classes that will require statecharts.
Identify all input messages across all sequence diagrams for the selected class.
For each selected class, make a list of all states you can identify( usually by
brainstorm)
Build statechart fragments and sequence the fragments in the correct order to form
statechart.
Review the paths and look for independent, concurrent paths.
Expand each transition with the appropriate message event, guard condition, and
action-expression. Include with each state appropriate internal transitions and
action-expressions.
Review and test(desk checking) each statechart.
Management information system 7_ 39 Huang Hong
