CS451 Introduction to Software Engineering

Behavioral Modeling

Behavioral Modeling

Outsideworld

Application

events behavior

Behavioral Modeling

• Make a list of the different states of a system (How does the system behave?)

• Indicate how the system makes a transition from one state to another (How does the system change state?)– indicate event– indicate action

• Draw a state transition diagram

The States of a System

• state—a set of observable circumstances that characterizes the behavior of a system at a given time

• state transition—the movement from one state to another

• event—an occurrence that causes the system to exhibit some predictable form of behavior

• action—process that occurs as a consequence of making a transition

State Transition Diagram Notation

statestate

new statenew state

event causing transitionevent causing transitionaction that occursaction that occurs

State Transition Diagram

readingreadingoperatoroperator

commandscommands

making copiesmaking copies reloading paperreloading paper

problem stateproblem state

fullfullinvoke read-op-inputinvoke read-op-input

full and startfull and startinvoke manage-copyinginvoke manage-copying

copies donecopies doneinvoke read-op-inputinvoke read-op-input

emptyemptyinvoke reload paperinvoke reload paper

jammedjammedinvoke problem-diagnosisinvoke problem-diagnosis

not jammednot jammedinvoke read-op-inputinvoke read-op-input

Control Model• TThe control flow diagram is "superimposed" on the DFD and he control flow diagram is "superimposed" on the DFD and

shows events that control the processes noted in the DFDshows events that control the processes noted in the DFD• CControl flowsontrol flows

– EEvents and control items—by dashed arrowsvents and control items—by dashed arrows– AA vertical bar implies an input to or output from a control vertical bar implies an input to or output from a control

spec (CSPEC) — a separate specification that describes spec (CSPEC) — a separate specification that describes how control is handledhow control is handled

– AA dashed arrow entering a vertical bar is an input to the dashed arrow entering a vertical bar is an input to the CSPECCSPEC

– AA dashed arrow leaving a process implies a data condition dashed arrow leaving a process implies a data condition– AA dashed arrow entering a process implies a control input dashed arrow entering a process implies a control input

read directly by the processread directly by the process• CControl flows do not physically activate/deactivate the ontrol flows do not physically activate/deactivate the

processes—this is done via the CSPECprocesses—this is done via the CSPEC

Control Flow Diagram

read operator

input manage copying

reload process

perform problem

diagnosis

create user

displays

empty

jammed

full

display panel enabled

beeper on/off

start

problem light

copies done

UML: Behavioral modeling

• Activity Diagrams

• Statechart Diagrams

• Interaction Diagrams

UML: State Diagram

Shows the behavior of one objectHow does it change its state based on the messages it receives, narrowly focused, fine-grained

• State: condition/situation during lifetime of an object • State transition: relationship indicating a state change (atomic & non interruptible)• Action: atomic & non-interruptible

Over drafted

ok

deposit

withdraw

deposit

withdraw

State notation (1)

• Substates: disjoint/concurrent• Entry/exit actions

– entry: an action that is performed on entry to the state

– exit: an action performed on exiting the state

• do: an ongoing activity performed while in the state (example: display window)– interruptible

• on: an action performed as a result of a specific event

State name

entry: entry action

exit: exit-action

do: activity-Aon: event-A: action-A

state variable(s)

State-A State-BEvent(arguments)[condition]/action

Transition notation (2)

• Event: significant occurrence that has a location in time and space– triggers the transition– signals, calls, passing of time, change in state

• Guard condition: • Transition only eligible to fire when guard evaluates to true• Guards of transition exiting one state are mutually exclusive

• Action: executable atomic computation

State diagram notation (3)

• Start state– No event triggers allowed – Branch conditions allowed– May not remain in start states

• End state– Top level end state terminates a state

machine

Initial state State-BEvent(attribute)

State transitions for an order

Checking

do: check item

Dispatching

do: initiate delivery

Waiting

Delivered

/ get first item

Item received[ some items not in stock ]

Item received[ all items available ]

Delivered

[ All items checked && some items not in stock ]

[ All items checked && all items available ]

get next item[ not all items checked ]

Example: Payment authorization in class Order

Authorizing

do: check payment

Authorized

Delivered

Rejected

[ payment ok ]

[ payment not ok ] 2 parallel processes:- authorization- order handling

Concurrent state diagram for the class Order

Checking

Waiting

Dispatching

Authorizing Authorized

Checking

Waiting

Dispatching

Authorizing Authorized

Cancelled

Delivered

Rejected

Statecharts

• Allow the decomposition of a model into sub-models

• A brief description of the actions is included following the ‘do’ in each state

• Can be complemented by tables describing the states and the stimuli

Full power

Enabled

do: operateoven

Fullpower

Halfpower

Halfpower

Fullpower

Number

TimerDooropen

Doorclosed

Doorclosed

Dooropen

Start

do: set power = 600

Half powerdo: set power = 300

Set time

do: get numberexit: set time

Disabled

Operation

Timer

Cancel

Waiting

do: display time

Waiting

do: display time

do: display 'Ready'

do: display 'Waiting'

Microwave Oven Model

Microwave oven state description

State Description

Waiting The oven is waiting for input. The display shows thecurrent time.

Half power The oven power is set to 300 watts. The displayshows ‘Half power’.

Full power The oven power is set to 600 watts. The displayshows ‘Full power’.

Set time The cooking time is set to the user’s input value. Thedisplay shows the cooking time selected and isupdated as the time is set.

Disabled Oven operation is disabled for safety. Interior ovenlight is on. Display shows ‘Not ready’.

Enabled Oven operation is enabled. Interior oven light is off.Display shows ‘Ready to cook’.

Operation Oven in operation. Interior oven light is on. Displayshows the timer countdown. On completion ofcooking, the buzzer is sounded for 5 seconds. Ovenlight is on. Display shows ‘Cooking complete’ whilebuzzer is sounding.

Microwave oven stimuli

Stimulus Description

Half power The user has pressed the half power button

Full power The user has pressed the full power buttonTimer The user has pressed one of the timer buttonsNumber The user has pressed a numeric keyDoor open The oven door switch is not closedDoor closed The oven door switch is closedStart The user has pressed the start buttonCancel The user has pressed the cancel button

Microwave oven operation

Cookdo: run generator

Done

do: buzzer on for 5 secs.

Waiting

Alarm

do: display event

do: checkstatus

Checking

Turntablefault

Emitterfault

Disabled

OK

Timeout

TimeOperation

Dooropen

Cancel