executable uml the models are the code - executable uml lecture 7 - getting a lifecycle paul krause

Executable UML

The Models are the Code -Executable UML

Lecture 7 - Getting a Lifecycle

Paul Krause

Executable UML

Lecture 7 - Getting a Lifecycle

Active Classes vs Passive Classes

Some basics of finite automata

How to use Statecharts properly

Completing the State model with State Transition Tables

Executable UML

Active vs Passive Classes

Active Classes The behaviour of instances of active classes

(“active objects”) varies over time e.g. Instances of a Thread class can be started,

paused, continued, stopped This behaviour can be captured in a Statechart

Passive Classes Passive objects have the same behaviour at all

times Operations on a class are sufficient to define its

behaviour Information classes, e.g. Address, are typically of

this kind

Executable UML

State

A condition or situation during the life of an object during which it satisfies some condition, performs some action, or waits for some event. The Unified Modelling Reference Manual

Executable UML

An Abstract Machine

Talkative Quiet

Happy

Chewing Gum

LiquoriceWine Gum

Executable UML

Finite Automata with Output

start

nocarry

0/1

owecarry

1/0

0/0, 1/1

1/0

0/1

Executable UML

Moore = Mealy

Mealy machine Actions are on the transitions (and only on the

transitions)

Moore machine Actions are on entry into new states (and only

on entry)

Both are computationally sufficient

Anything that can be expressed as a Moore machine can be expressed as a Mealy machine, and vice-versa

Executable UML

UML Statechart Notation

e1 [cond] / action1;action2

event name

guardcondition actions

StateA

entry/ actionsexit/ actions

StateB

entry/ actionsexit/ actions

Executable UML

What Happens?

e1 [y < 10] / x = 5StateA

exit/ x = 10

StateB

entry/ actionexit/ action

e1 [x < 10] / y = 5StateC

exit/ y = 10

StateD

entry/ actionexit/ action

initially x = 0 & y = 0

Executable UML

Good Practice for Statecharts

Express the behaviour of Active Classes using a Statechart for each active class

Restrict usage to a subset of the full Statechart notation for clarity: Actions are specified on entry into a state (not

on exit, or on the transition itself) An individual event can only cause a single

transition out of a given state

This usage corresponds to expressing behaviour as a “Moore” machine

Executable UML

State-dependent behaviour

Stopped

entry/

Moving

entry/

Emergency stopin progressentry/

apply emergency brake

Stopped forEvacuationentry/open all doorssound alarm

trainStopped

fireDetected

trainStartedtrainStopped

fireDetected

trainMadeSafe

Executable UML

Including state-independent behaviour

Stopped

entry/

Moving

entry/

Emergency stopin progressentry/

apply emergency brake

Stopped forEvacuationentry/open all doorssound alarm

trainStopped

fireDetected

trainStartedtrainStopped

fireDetected

trainMadeSafe

Updating fuelwhile stopped

entry/

this.fuelLevel = fuelLevel

Updating fuelduring emergency

entry/


Updating fuel duringemergency stop

entry/


Updating fuelwhile moving

entry/


trainMadeSafe

trainStopped fuelLevelUpdated

fireDetected

fireDetected

fuelLevelUpdated

trainStopped

fuelLevelUpdated

trainStarted

Executable UML

State-independent behaviour

Executable UML

Ideal Class representation

Aircraft

registrationNoairframeNoaltitudelatitudelongitude

createAircraftgetPosition

takeOffClearanceGrantedlandingClearanceGrantedreadyForDepartureaircraftClearedRunway

Name Compartment

Attribute Compartment

Operation Compartment

Signal Compartment

Executable UML

State model for Aircraft Class

Flying

Landing

On Ground

Waiting for Clearanceto Take-Off

Taking OfflandingClearanceGranted

aircraftClearedRunway

readyForDeparture

takeOffClearanceGranted

aircraftClearedRunway

In most UML tools, this is the placewhere the signal events associated witha class are recorded.

Executable UML

Microwave Oven - being more systematic

When the door is closed and the button pressed, the oven cooks for 1 minute

The light is on when cooking or when the door is open

Further button presses increase the cooking time by 1 minute each

When the timer times out, the power tube and light are turned off and a warning beep is emitted

MicrowaveOven

manufacturerserialNumber {I}lightOndoorOpenpowerTubeEnergizedcookingTimeRemaining

Executable UML

Events and Actions

Signals or Events

doorOpened

doorClosed

buttonPressed

timerTimesOut (counts down to zero)

Actions

Turn on the light

Turn off the light

Energize the power tube

De-energize the power tube

Set the timer for 1 min.

Add 1 min. to the timer

Clear the timer

Sound the beeper

Executable UML

First version of Statechart

4. CookingInterruptedentry/turn off lightde-energize power tubeclear timer

5. Cooking Complete

entry/turn off lightde-energize power tubeclear timer

3. Cooking

entry/turn on lightenergize power tubeset timer for 1 minute

2. Door Open

entry/turn on light

1. Ready to Cook

entry/turn off light

doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

The numbering does notimply any sequencing

Executable UML

The Statechart is not a complete model


5. Cooking Complete


3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

What happens if wepress the button whencooking is complete?

What happens if wepress the button while

cooking?

What happens if wepress the button when

the door is open?

Can a door closed eventbe generated when

the door is already closed?

Executable UML

State Transition TablebuttonPressed

doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open

Cooking Cooking Interrupted

Cooking Complete

Cooking Complete

Door Open

Cooking Interrupted

Door Closed

Door Open

Door Closed

Executable UML


doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open

Cooking Cooking Interrupted

Cooking Complete

Cooking Complete

Cooking Door Open

Cooking Interrupted

Door Closed

Door Open

Door Closed

Executable UML

New Transition


5. Cooking Complete


3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

buttonPressed

Executable UML


doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open

Cooking Cooking? Cooking Interrupted

Cooking Complete

Cooking Complete

Cooking Door Open

Cooking Interrupted

Door Closed

Door Open

Door Closed

Executable UML

Is this correct?


5. Cooking Complete


3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

buttonPressed

buttonPressed

Executable UML

Discovering new states and events


5. Cooking Completeentry/turn off lightde-energize power tubeclear timer

3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

buttonPressed

6. CookingExtendedentry/add 1 min. to timer

buttonPressed

timerTimesOut

doorOpened

buttonPressed

Executable UML


doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open

Cooking Cooking Extended

Cooking Interrupted

Cooking Complete

Cooking Complete

Cooking Door Open

Cooking Interrupted

Door Closed

Door Open

Door Closed

Cooking Extended

Cooking Extended

Cooking Interrupted

Cooking Complete

Executable UML

Event ignored



3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

buttonPressed


buttonPressed

timerTimesOut

doorOpened

buttonPressed

buttonPressed event willhave no effect

buttonPressed eventwill have no effect

timerTimesOut eventwill have no effect

Executable UML


doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open Event Ignored


Cooking Interrupted

Cooking Complete

Cooking Complete

Cooking Door Open

Cooking Interrupted

Event Ignored Door Closed

Event Ignored

Door Open

Event Ignored Door Closed

Cooking Extended

Cooking Extended

Cooking Interrupted

Cooking Complete

Executable UML

Can’t Happen



3. Cooking


2. Door Open

entry/turn on light

1. Ready to Cook


doorClosed

doorOpened

doorOpened

buttonPressed

timerTimesOut

doorOpened

doorClosed

buttonPressed


buttonPressed

timerTimesOut

doorOpened

buttonPressed

another doorOpen eventcan’t happen here!

another doorClosed eventcan’t happen here!

Executable UML


doorOpened

doorClosed

timerTimesOut

Ready to Cook

Cooking Door Open Can’t Happen

Event Ignored


Cooking Interrupted

Can’t Happen

Cooking Complete

Cooking Complete

Cooking Door Open Can’t Happen

Can’t Happen

Cooking Interrupted

Event Ignored Can’t Happen

Door Closed

Event Ignored

Door Open

Event Ignored Can’t Happen

Door Closed

Can’t Happen

Cooking Extended

Cooking Extended

Cooking Interrupted

Can’t Happen

Cooking Complete

Executable UML

Practical benefits for Testing

Writing out the State Transition table helps identify missing transitions We found one major fault in the first Philips DVD

player in this way, even before executing the test cases

Each cell in the table is a potential test case. However, remember:

You do need to execute “Event Ignored” tests

You do not need to execute “Can’t Happen” tests in fact you will be physically unable to!

Executable UML

Summary

We have seen how Statecharts can be used to model the lifecycles of class instances

Restricting usage of full UML to a precise subset adds clarity to the models, but

Statecharts are an incomplete view of the full state behaviour Use State Transition Tables to help identify

missing transitions and states Base your test cases on the State Transition

Tables and not on the Statechart

See Chapter 9 of Mellor and Balcer

executable uml the models are the code - executable uml lecture 7 - getting a lifecycle paul krause

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