lecture09-sequencediagrams

7/25/2019 lecture09-sequencediagrams

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UML Sequence Diagrams

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UML sequence diagrams

sequence diagram: an "interaction diagram" thatmodels a single scenario executing in the system perhaps 2nd most used UML diagram (behind class diagram)

relation o UML diagrams to other exercises: !! cards #$ class diagram

use cases #$ sequence diagrams


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%ey parts o a sequence diag&

participant: an ob'ect or entity that acts in thesequence diagram sequence diagram starts ith an unattached "ound message"

arro

message: communication beteen participant ob'ects

the axes in a sequence diagram: horiontal: hich ob'ect*participant is acting

+ertical: time (don #$ orard in time)


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Sequence dg& rom use case


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epresenting ob'ects

Squares ith ob'ect type, optionally preceded by ob'ectname and colon rite ob'ect-s name i it clariies the diagram ob'ect-s "lie line" represented by dashed +ert& line


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message (method call) indicated by horiontalarro to other ob'ect rite message name and arguments abo+e arro

Messages beteen ob'ects


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Messages, continued

message (method call) indicated by horiontalarro to other ob'ect dashed arro bac. indicates return dierent arroheads or normal * concurrent

(asynchronous) methods


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Lietime o ob'ects

creation: arro ith -ne-ritten abo+e it notice that an ob'ect created

ater the start o the scenarioappears loer than the

others

deletion: an / at bottom oob'ect-s lieline

0a+a doesn-t explicitly deleteob'ects1 they all out oscope and are garbage#collected


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ndicating method calls

activation: thic. box o+er ob'ect-s lie line1 dranhen ob'ect-s method is on the stac. either that ob'ect is running its code, or it is on the stac.

aiting or another ob'ect-s method to inish

nest to indicate recursion

Activation

Nesting


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ndicating selection and loops

rame: box around part o a sequence diagram to indicateselection or loop if #$ (opt) 3condition4 if/else #$ (alt) 3condition4, separated by horiontal dashed line loop #$ (loop) 3condition or items to loop o+er4


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lin.ing sequence diagrams

i one sequence diagram is too large or reers to another diagram,indicate it ith either: an uninished arro and comment a "re" rame that names the other diagram hen ould this occur in our system5


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6xample sequence diagram


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7orms o system control

8hat can you say about the control lo o each o theolloing systems5 s it centralied5 s it distributed5


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7laed sequence diagram 9

8hat-s rong ith this sequence diagram5 (Loo. at the UMLsyntax and the +iability o the scenario&)


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7laed sequence diagram 2

8hat-s rong ith this sequence diagram5


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8hy not 'ust code it5

Sequence diagrams can be somehat close to the codele+el& So hy not 'ust code up that algorithm ratherthan draing it as a sequence diagram5

a good sequence diagram is still a bit abo+e the le+elo the real code (not all code is dran on diagram)

sequence diagrams are language#agnostic (can be

implemented in many dierent languages non#coders can do sequence diagrams easier to do sequence diagrams as a team can see many ob'ects*classes at a time on same

page (+isual bandidth)


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Sequence diagram exercise 9

Let-s do a sequence diagram or the olloing casualuse case, Start New Poker Round :

he scenario begins hen the player chooses to start a neround in the U& he U as.s hether any ne players ant to

'oin the round1 i so, the ne players are added using the U&

;ll players- hands are emptied into the dec., hich is thenshuled& he player let o the dealer supplies an ante bet othe proper amount&


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Sequence diagram exercise 2

Let-s do a sequence diagram or the olloing casualuse case,Add Calendar Appointment : he scenario begins hen the user chooses to add a neappointment in the U& he U notices hich part o the calendar isacti+e and pops up an ;dd ;ppointment indo or that date and time& he user enters the necessary inormation about the appointment-sname, location, start and end times& he U ill pre+ent the user romentering an appointment that has in+alid inormation, such as an emptyname or negati+e duration& he calendar records the ne appointmentin the user-s list o appointments& ;ny reminder selected by the user isadded to the list o reminders&

the user already has an appointment at that time, the user isshon a arning message and as.ed to choose an a+ailable time orreplace the pre+ious appointment& the user enters an appointmentith the same name and duration as an existing group meeting, thecalendar as.s the user hether he*she intended to 'oin that groupmeeting instead& so, the user is added to that group meeting-s list o

participants&

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lecture09-sequencediagrams