Wk5_UML_ActivityDiagram.pptx

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UML Activity Diagrams
6 October 2008

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Example

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Activity Diagram: what is it?
• Describes activities and flows of data or
decisions between activities
• Provides a very broad view of business
processes
• Can be used to break out the activities
that occur within a use case
• Good for showing parallel threads

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Activity Diagram: when to use it?
• When describing work flow across many use
cases
• When analysing a use case, and before
methods are assigned to symbols
• When dealing with multi-threaded applications

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Creating an Activity Diagram
This diagram is useful in showing work flow
connections and describing behaviour that has a
lot of parallel processing.
When you use an activity diagram you can choose
the order in which to do things.
It expresses the essential sequencing rules to
follow.
It is different from a flow chart in that it shows
parallel processes, not just sequential processes.

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Activity Diagram
• Shows a set of activities, the flow from activity
to activity.
• Represents the dynamic view of a system.
• Models the function of a system.

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Activity Diagram
• Activity diagrams show the flow of control
between activities
– They can model the sequential and concurrent
steps in a computational process
– They can also model the flow of an object as it
moves from state to state at different points in the
activity

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UML Activity symbols
ActionState initial state final state
Transition
(Fork)
Transition
(Join)
Control Flow
Decision
Swimlane

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Action State
• In a conceptual diagram an activity is a task that
needs to be done – either by a human or a
computer
• In a specification-perspective diagram or an
implementation-diagram, an activity is a method
on a class

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Sequential Branching
• A sequential branch is represented as a diamond
– It may have one incoming transition and two or more
outgoing transitions
– Guards are associated with each transition. The guards
are evaluated upon entering the branch, and the one
that evaluates to true is then taken

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Branch & Merge
Calculate Risk
Issue a Loan
[ risk low]
Ask for Authorization
Continue
[ risk high]

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Forking and Joining
• Concurrent activities within an activity diagram are modelled
with the use of synchronised bars
• Synchronisation bars are drawn as a thick horizontal or vertical
line
• Joins and Forks should balance
– The number of flows that leave a fork should equal to the number
of flows entering the corresponding join.

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Fork & Join
Issue a Loan
Reserve Money Make a Agreement
Make an Offer

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PrepareMeal
CookSpaghetti MakeSauce
Combine
OpenBottleWine
[ in the mood for wine]
Serve

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Forks, Joins & conditional Threads
PrepareMeal
CookSpaghetti MakeSauce
Combine
OpenBottleWine
Serve
[ in the mood for wine]

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Swim lanes
• The activities of an activity diagram may be performed by
different groups.
• Each zone or lane represents the responsibilities of a particular
group.
• If swimlanes are used, each activity can belong to one and only
one swimlane.
• To use swimlanes, you must arrange your activity diagrams into
vertical zones separated by dashed lines.

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Swim lanes
Administration
Desk
Finance
Issue a Loan
Reserve Money Make a Agreement
Make an Offer

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Activity
Diagram

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Composite Activity

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Receive Order
Assign Goods to item
Authorize Payment
[ for each line item] /
Cancel Order
[ failed]
*
Reorder Goods
[ need to order]
[ succeeded]
Dispatch Order
[ stock assigned to all items and payment authorized]

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Object Flow
• Objects may be involved in the flow of control associated with an
activity.
– These associations can be shown in activity diagrams by placing objects
in the diagram and linking them to specific activities using a dependency
link.
– The same object may be the output of one action and the input of one or
more subsequent activities.
– To distinguish the various appearances of the same object, the state of
the object at each point may be placed in brackets and appended to the
name of the object.

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Object
Flow
Example
Stockroom
Sales
Customer
Request service
Take order
Fill order
Deliver order
Pay
Take order
Stockroom
Sales
Customer
Request service
Take order
Fill order
Deliver order
Pay
Collect order
Order [placed]
Order [entered]
Order [filled]
Order [delivered]

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Date2date example: scenario’s
Use case
Log in Subscriber
Step-by-step Plan
1. Validate number of invalid login’s
2. If number of invalid login’s more than 2, stop
3. Show web-page
4. Actor enters login and password
5. Actor confirms login
6. Application validates login
7. If login is valid
7.1 Actor is marked as subscriber
7.2 Stop
8. If login is invalid
8.1 Increase the number of steps
8.2 Repeat from 1.

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Use Case Log in subscriber
Actors Subscriber, Visitor
Description
Pre-conditions
Check validity actor as subsciriber
----
Basic flow 1. Validate number of invalid login’s
2. Show web-page
3. Actor enters login and password
4. Actor confirms login
5. Application validates login
6. Actor is marked as subscriber
Extension /
Exception flow 1a Login is invalid
1a1 Number of logins >2, stop
5a Login is invalid
5a1 Increase number of logins, repeat 1
Post-conditions Actor is known as subscriber and actor is logged in
Date2date : Log in Subscriber – use case text

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Date2date :
Log in
subscriber –
activity diagram

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Key point
• Activity diagrams are useful for
– Business Process Redesign
– Work Flow Modelling
– Analysing Use Cases

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NS Ticket service
• Define a use case diagram of
‘NS Ticket service’
• Describe an use case.
Take ticket
Destination
Single / Retour
No Reduction /
40% reduction
2e class / 1e class

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Use Case diagram ‘NS Ticket service’
Traveller
Buy OV ticket
Buy NS ticket
Pay ticket
«extends»
«uses»

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Use Case Buy OV Ticket
Actors Traveller
Preconditions Traveller has a valid pass
Description 1. Ticket device expects destination code
2. Traveller enters destination code
3. Extension point: NS ticket
4. Ticket device checks code and calculates the charge. Shows
destination code & fare. Activates ticket machine for paying
5. Traveller pays (use case: Pay ticket)
6. Ticket device print and supplies ticket
7. Traveller takes ticket
Extension Destination code = NS station.
3a. Ticket device expects ticket type
3b. Traveller enters Single/Return, Discount Y/N, Class
Exceptions Traveller interrupt the interaction or walk away
Traveller enters an incorrect destination code
Payment is not finished off successful
Result Traveller has ticket.
(NS can look forward to the payment)

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Make a class diagram of ‘NS ticket service’
including the classes ‘Ticket’ and
‘Destination’
+create()
+payPrice()
+printTicket()
-fromStation
-toStation
-oneWay : Boolean
-reduction : Boolean
-class
-date : Date
-price : Currency
Ticket
+validateDestination()
+showPrice()
-code
-name
-distance
-base price
Destination
+Print()
+checkStatusPrinter()
-statusPrinter
Printer
* 1

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Make an activity diagram for the actor ‘Traveller’
Enter Destination
[else] [ correct NS destination]
Choose single or return Choose reduction Y/N Choose 1st / 2snd class
[ bus&tram card]
Pay ticket
[ payment not OK]
Take ticket
[ else]

Wk5_UML_ActivityDiagram.pptx

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Wk5_UML_ActivityDiagram.pptx