Pemodelan Kebutuhan
Pendekatan Berorientasi Objek
Fajar Pradana S.ST., M.Eng
Tujuan perkuliahan
• Memahami konsep pendekatan berorientasi objek dalam
pemodelan kebutuhan
Agenda
• Konsep pemodelan berorientasi objek
• Elemen-elemen pemodelan berorientasi objek
• Dokumentasi dan alat bantu
Object Oriented Approach
• Mulai populer akhir ’80an – ’90an (Booch, Rumbaugh-OMT, Jacobson-OOSE, Coad+Yourdon, Wirfs-Brock) :
▪ Elisitasi kebutuhan customer
▪ Identifikasi skenario / use-case (use-case diagram)
▪ Identifikasi klas berdasarkan kebutuhan customer
▪ Identifikasi atribut dan operasi setiap klas
▪ Definisi struktur klas (class diagram)
▪ Definisi model relasi antar klas (collaboration/sequence diagram)
▪ Definisi perpindahan status sistem (statechart diagram)
• 1996 : UML (Unified Modeling Language) – Grady Booch+James
Rumbaugh+Ivar Jacobson
Keuntungan
• Sangat natural, sesuai dengan cara berpikir manusia improve analyst and problem domain expert interaction
• Meningkatkan konsistensi hasil analisis abstraksi atribut-operasi dalam sebuah objek
• Konsep penurunan klas memberikan kemudahan dalam generalisasi objek
• Kemudahan dalam perubahan
• Terjaganya konsistensi model antara analisis dan perancangan
• Konsep reusability
Object, Class – Apa Itu ?
• Objek (Object) :
▪ A concept, abstraction, or thing with crisp boundaries and meaning for the problem at hand [Rumbaugh]
▪ Benda (tangible & intangible thing)
▪ Contoh : Andi, Eko, Susi (sistem akademik)
▪ Sebuah objek memiliki karakteristik : identity (identitas-pembeda), state (sekumpulan atribut) & behaviour (sekumpulan operasi, aksi, servis)
• Notasi :
Nama Objek
Atribut2
Operasi2
Object, Class – Apa Itu ?
• Klas (Class) :
▪ A description of one or more objects with a uniform set of attributes and services, including a description of how to create new objects in the class [Yourdon]
▪ Gambaran umum (template, blue-print) yang menjelaskan
sekumpulan objek yang memiliki kesamaan karakteristik (atribut dan operasi)
▪ Merupakan cetakan dari objek
▪ Digunakan untuk menginstansiasi objek yang memiliki identitas yang berbeda
▪ Contoh : Klas Mahasiswa objek Andi, Eko, Susi
▪ Abstract & concrete class
Object, Class – Apa Itu ?
Mahasiswa
- NIM
- Nama
- Buat skripsi
- Ujian
Mahasiswa
- NIM : 001
- Nama : Andi
- Buat skripsi
- Ujian
Mahasiswa : Andi
Mahasiswa
- NIM : 002
- Nama : Eko
- Buat skripsi
- Ujian
Mahasiswa : Eko
Mahasiswa
- NIM : 003
- Nama : Susi
- Buat skripsi
- Ujian
Mahasiswa : Susi Instansiasi :
penciptaan objek
Where to look ?
• Investigasi domain masalah
• Langkah-langkah:
▪ Observe first-hand observasi langsung ke lap.
▪ Actively listen to problem domain experts what, who, why, when and how
▪ Check previous OOA results
▪ Check other systems comparison
▪ Read, read, read getting some more information
What to look for ? Nouns
• Structures
▪ Relasi antar objek -> generalisasi, agregasi
• Other systems
▪ Sistem lain yang berinteraksi dg proposed system
• Things or events remembered
▪ Data, status, kejadian yang harus disimpan
• Roles played
▪ Identifikasi peran manusia dalam sistem -> berinteraksi langsung, tidak berinteraksi tetapi informasinya disimpan sistem
• Sites
▪ Informasi lokasi/posisi yang harus diingat oleh sistem
Identifikasi atribut
• Some data (state information) for which each object in a class has its own value [Yourdon]
• Langkah-langkah:
▪ Identifikasi atribut umum (adjectives, possessives)
▪ Identifikasi atribut yang relevan dg domain masalah
▪ Identifikasi atribut yang relevan dg peran atau tanggung jawab dalam sistem
▪ Restrukturisasi atribut sehingga atomic kemudahan
▪ Reposisi atribut yang sesuai dengan hirarki klas nya pewarisan klas
▪ Spesifikasi atribut presisi, nilai default, batasan, dll.
Identifikasi operasi/servis
• A specific behavior that an object is responsible for exhibiting [Yourdon]
• Langkah-langkah:
▪ Identifikasi tanggung jawab umum sebuah klas (verbs)
▪ Identifikasi operasi yang spesifik untuk domain masalah
▪ Identifikasi operasi yang relevan dg peran atau tanggung jawab dalam sistem
▪ Spesifikasi operasi argumen, batasan/aturan, logika/algoritma
Diagram UML
• Use-case diagram (statis)
• Class diagram (statis)
• Collaboration/sequence diagram (dinamis)
• Statechart diagram (dinamis)
Use Case Diagram
• Menjelaskan perilaku sistem dari tampak luar
• Menyediakan fungsi-fungsi yg harus dipenuhi sistem sesuai dengan aktornya
• Elemen: actor (orang, sistem lain) dan use-case
• Setiap use-case dilengkapi dengan skenario (deskripsi)
• Langkah-langkah:
▪ Identifikasi aktor
▪ Identifikasi use-case per aktor
Use Case Diagram
Select product
Get return coins Customer
Enter object
Use-case scenario
Flow of events for the Select product use-case
Objective Allow customer to select a certain product to dispense
Actors Customer
Pre-condition Coin detected and valid
Main flow 1. The customer selects a button product.
2. The system displays an entry prompt of number of product to order.
Alternative flows 1. If the selected product is not available, the system will display a message “Your selected product is not available”.
2. If the selected product is available but there isn’t enough number to order, the system will display a message “The number isn’t enough, max. x”. X is the existing number of the product.
Post-condition The selected product dispensed as the number needed
Use-case association
• Include
▪ A use case uses another use case (functional decomposition) reuse
▪ A function in the original problem statement is too complex to be solvable immediately describe the function as the aggregation of a set of simpler functions (mandatory)
• Extend
▪ A use case extends another use case
▪ The functionality in the original problem statement needs to be extended
▪ The extended use-case plays an optional use-case
<<include>> and <<extend>>
ViewMap OpenIncident
AllocateResources
<<include>>
<<include>>
Base Use
Case Supplier
Use Case
ReportEmergency
Help
<<extend>>
A
B Base Use
Case
Actor-generalization
• Two/more sub-actors generalized into a super-actor
• Have both behavior and attributes in common – described under the super-actor
• Super-actor should interact with use cases when ALL of its sub- actors interact in the same way
• Sub-actors should interact with use cases when their individual
interactions differ from that of the super-actor
Actor-generalization
Class diagram
• Menggambarkan struktur statis dari sistem
• Terdiri dari node (klas) dan relasi
• Jenis relasi
▪ Generalization (‘is a’ – inheritance)
▪ Association
▪ Aggregation (‘part-of’)
▪ Composition
Association
• For “real-world objects” is there an association between classes?
• Classes A and B are associated if:
▪ An object of class A sends a message to an object of B
▪ An object of class A creates an instance of class B
▪ An object of class A has an attribute of type B or collections of objects of type B
▪ An object of class A receives a message with an argument that is an instance of B (maybe…) will it “use” that argument?
• Does an object of class A need to know about some object of class
B?
Aggregation – composition
• Aggregation represents a part-whole or part-of relationship
• Aggregation can occur when a class is a collection or container of other classes, but where the contained classes do not have a strong life cycle dependency on the container – essentially, if the container is destroyed, its contents are not
• Composition is more specific than aggregation
• Composition usually has a strong life cycle dependency between
instances of the container class and instances of the contained
class(es) if the container is destroyed, normally every instance
that it contains is destroyed as well
Class relationships – examples
Class stereotypes
• Boundary classes
▪ model the interaction and manage communication between the computer system and its actors, but don’t directly represent the specific interface object in the implementation
▪ used to identify the main logical interfaces with users and other systems (including e.g. other software packages, printers)
▪ main task is to translate information across system boundaries
▪ partition the system so that interface is kept separate from business logic
Class stereotypes
• Entity classes
▪ used to model data and behavior of some real life system concept or entity e.g. member, bank account, order, employee
▪ these will sometimes require more persistent storage of information e.g. a student’s details are ultimately stored as a student record
• Control classes
▪ represent coordination, sequencing, transactions and control of other objects
▪ glue between boundary elements and entity elements, describing the logic required to manage the various elements and their interactions
▪ roughly one per use case
Class stereotypes
Actor 1
<<boundary>>
<<control>>
<<boundary>>
<<entity>> <<entity>>
Actor 2
boundary entity control
Sequence diagram
• An interaction diagram that emphasizes the time ordering of messages
• Shows a set of objects and the messages sent and received by those objects
• Elements
▪ Object represented in a box
▪ Dashed line called the object lifeline, and it represents the existence of an object over a period of time
▪ Message rendered as horizontal arrows being passed from object to object as time advances down the object lifelines
Sequence diagram – example
: Customer : SelectionScreen : SelectionController : Products :
DispenserProduct
selectProduct( )
getValidSelection(String)
isProductAvailable(String)
dispenseProduct(String, int)
Statechart diagram
• A statechart diagram shows the behavior of classes in response to external stimuli
• This diagram models the dynamic flow of control from state to
state within a system
Statechart diagram – example
Waiting for a coin
Waiting for selection
Dispensing product
Returning payment initial
accept new coin
payment returned accept new coin coin detected
accept customer request product dispensed
accept new coin
sufficient payment dispense product
product available=FALSE
return payment coin return request
return payment
Alat Bantu
• Structured Analysis :
▪ Aplikasi pengolah model : Visio, dll.
▪ Aplikasi pengolah kata : MS Word, dll.
▪ CASE Tool : StP (Software through Picture), PSL/PSA (Problem
Statement Language/Problem Statement Anaylzer), ILeaf, SPMS, dll.
• OO Analysis :
▪ Aplikasi pengolah model : Visio, dll.
▪ Aplikasi pengolah kata : MS Word, dll.
▪ CASE Tool : Rational RequisitePro, Rational Soda for Word, Rational Rose, ArgoUML, dll.
Dokumentasi
• Introduction
▪ 1.1. Purpose of the requirements document
▪ 1.2. Scope of the product
▪ 1.3. Definition, acronyms and abbreviations
▪ 1.4. References
• General Description
▪ 2.1. Product perspective
▪ 2.2. Product functions
▪ 2.3. User characteristics
▪ 2.4. General constraints
• Specific Requirements
▪ All functional and non-functional requirements, system models (eg. DFD/CFD, ERD, STD, Use-Case, Class, Sequence, Statechart diagrams), performance, database requirements, design constraints, security.
• Qualification/Validation Requirements
• Appendices/Bibliography
