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The OOA Process - II. Scenarios. The Steps of OOA - Part 1. identify objects (classes) identify structures generalization - specialization (“ISA”) whole - parts (“PART-OF”) association (relationship) define attributes ===> Static Objectdiagram ===> incomplete Object Dictionary.

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The OOA Process - II

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The ooa process ii l.jpg

The OOA Process - II

Scenarios


The steps of ooa part 1 l.jpg

The Steps of OOA - Part 1

  • identify objects (classes)

  • identify structures

    • generalization - specialization (“ISA”)

    • whole - parts (“PART-OF”)

    • association (relationship)

  • define attributes

    ===> Static Objectdiagram

    ===> incomplete Object Dictionary


The steps of ooa part 2 l.jpg

The Steps of OOA - Part 2

  • define services via scenarios

    • services per object

    • message passing between objects

    • coordination of message passing

    • states and transitions

      ===> Scenarios

      ===> complete Object Dictionary


Ooa messages l.jpg

OOA - Messages

sender

  • form the dynamic portion

    of the object diagram (scenarios)

  • sent by

    • an object (instance)

    • via an active local service

  • received by

    • an object (instance)

    • triggering the receiving service

label

receiver


A message s life cycle l.jpg

A Message’s “Life-Cycle”

  • connects to an object(object_id).service

  • triggers execution of the receiving service

  • carries input-parameters for the execution of the receiving service

  • is able to transmit output-parameters back to the sending service


Message specification l.jpg

Message Specification

  • scenarios (diagrams):

    • shown as bold or dotted line

    • label is optional

    • parameters are optional

    • sequence number is optional

  • object dictionary:

    • exist only as elements of an object’s services

    • specified as part of the service specifications


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Syntax for Message Specification

  • typically similar to:

    SEND MESSAGE TO

    object (object_id).service

    (input-parameters, output-parameters)

    • object: name of an object class

    • service: name of a service in that object class

    • object_id: identifies selected instantiation (structures, especially associations!)


Slide8 l.jpg

The division wants to

compile a list of the

prg. languages “spoken”

in its departments.

Division

(2,N)

(1,1)

Programmer

Department

list of prog-lang.

(1,1)

(3,N)

works-for


Slide9 l.jpg

Division

Alternative 1:

Using output-parameters

to get to the results.

report prg-langs

list prg-skills

(wait for result)

Programmer

Department

list prg-lang

(wait for result)

list prg-lang

list prg-skills


Slide10 l.jpg

Alternative 2:

Using separate messages

to transmit results.

Division

report prog-langs

accept prg-lang

accept prg-lang

list prg-skills

(do not wait for result)

Programmer

Department

list prg-lang

(do not wait

for result)

list prg-langs

list prg-skills


Ooa services l.jpg

OOA - Services

  • exist only as elements of an object

  • services model functionality:

    • data manipulation

    • control sequences

    • communication (using messages)

    • state transformation

    • interface handling


Ooa services12 l.jpg

OOA - Services

  • no separate graphical representation

    (part of the object symbol)

  • services can be

    • public or

    • private

  • specified in the object dictionary


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Attributes and Services

  • the data capsule principle

    • a service has access to all attributes of the local object

    • all services of an object share attributes as a global data area

    • a service provides access to attributes for other object.services (by accepting messages)

    • a service can have local variables


Services and inheritance l.jpg

Services and Inheritance

  • are inherited in a classification hierarchy

  • inheritance is mandatory

  • multiple inheritance is possible

    => position common services as high in

    the classification hierarchy as possible

    => generic services / service overlay /

    polymorphism


Slide15 l.jpg

Employee

Inheritance

fill-in time-sheet

prepare paycheque

Manager

Programmer

fill-in time-sheet

fill-in time-sheet

list prg-langs


Scenarios l.jpg

Scenarios

  • show separate self-contained sequences (threads) of execution in separate diagrams

  • include

    • objects

    • messages

    • (services)

    • (attributes)

  • do usually not include

    • structures


Slide17 l.jpg

hire (2)

Division

create (1)

Department

Manager

Programmer

Scenario 1:

“Open a new department”

hire (3)


Slide18 l.jpg

Scenario 2 (Alternative 2):

“Prepare list of prog.

languages for divison.”

Division

report prog-langs

accept prg-lang

accept prg-lang

list prg-skills

(do not wait for result)

Programmer

Department

list prg-lang

(do not wait

for result)

list prg-langs

list prg-skills


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