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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-5

    Simbol Dasar

    Empat Simbol Dasar

    Kotak rangkap dua digunakan untukmenggambarkan suatu entitas eksternal (bagian

    lain, suatu perusahaan, seseorang, atau sebuahmesin) yang dapat mengirim data atau menerimadata dari sistem

    Tanda panah menunjukkan perpindahan data dari

    satu titik ke titik yang lain Bujur Sangkar dengan sudut membulat digunakan

    untuk menunjukkan adanya proses transformasi

    Bujur sangkar dengan ujung terbuka yang

    menunjukkan penyimpanan data

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    7/45Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-7

    Entitas Eksternal

    Entitas Eksternal mungkin

    orang, seperti CUSTOMER atau STUDENT

    Sebuah perusahaan atau organisasi,seperti BANK atau SUPPLIER

    Departemen lain di dalam perusahaan

    seperti ORDER FULFILLMENTSistem atau subsistem lainnya seperti

    INVENTORY CONTROL SYSTEM

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    Proses

    Mewakili baik:

    Keseluruhan sistem

    sebuah subsystem

    Pekerjaan yang diselesaikan, sebuah aktifitas

    Nama harus dalam bentuk kata kerja-kata benda- kata sifat

    Kata kerja menggambarkan jenis kegiatan seperti menghitung,menverifikasi, menyiapkan, mencetak atau menambahkan. Katabenda menunjukkan hasil utama proses seperti laporan, record.Kata Sifat mengilustrasikan keluaran yang mana seperti urutan ke

    belakang atau inventarisasi. Contoh nama-nama proses yang lengkap ialah menghitung pajak

    penjualan, memverifikasi status rekening konsumen, menyiapkaninvoice pengapalan, mencetak laporan yang diurutkan ke belakang,mengirim konformasi email ke konsumen, memverifikasi neracakartu kredit, menambah record inventaris

    1

    Add NewCustomer

    2

    CustomerInquiry

    Subsystem

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    Penyimpanan Data

    Nama dengan sebuah kata benda, menggambarkandata

    Penyimpanan data biasanya diberikan sebuah nomorreferensi unik seperti D1, D2, D3

    Termasuk dalam penyimpanan data seperti:

    Sebuah File Komputer atau database

    Sebuah File Transaksi Sebuah kumpulan tabel

    Sebuah file record manual

    D1CustomerMaster

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    Aliran Data

    Menunjukkan data tentang orang, tempat,atau sesuatu bergerak diantara sistem

    Nama harus sebuah benda menggambarkanpergerakan data di antara sistem

    Kepala panah menunjukkan arah aliran

    Gunakan double headed-arrows hanya ketikasebuah proses membaca data danmengupdate data pada tabel atau file yangsama

    Customer Record

    New Customer

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    11/45Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-11

    Developing Data FlowDiagrams

    Use the following guidelines:

    Create the context level diagram, including

    all external entities and the major dataflow to or from them

    Create Diagram 0 by analyzing the major

    activities within the context processInclude the external entities and major data

    stores

    Create a child diagram for each complex

    process on Diagram 0

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    Creating Data Flow Diagrams

    Detailed data flow diagrams may bedeveloped by

    Making a list of business activities

    Analyzing what happens to an input dataflow from an external entity

    Analyzing what is necessary to create anoutput data flow to an external entity

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-14

    Data Flow Diagram Levels

    Data flow diagrams are built in layers

    The top level is the Context level

    Each process may explode to a lowerlevel

    The lower level diagram number is thesame as the parent process number

    Processes that do not create a childdiagram are called primitive

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-16

    Diagram 0

    Diagram 0 is the explosion of thecontext level diagram

    Should include up to 7 or 9 processes

    Any more will result in a cluttered diagram

    Processes are numbered with an integer

    The major data stores and all externalentities are included on Diagram 0

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-18

    Child Diagrams

    Each process is numbered with theparent diagram number, a period, and a

    unique child diagram numberExamples are:

    3.2 on Diagram 3, the child of process 3

    5.2.7 on Diagram 5.2, child of process 5.2

    On Diagram 3, the processes would benumbered 3.1, 3.2, 3.3 and so on

    3.2

    Edit

    Customer

    5.2.7

    CalculateCustomer

    Discount

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-19

    Child Diagrams

    External entities are usually not shownon the child diagrams below Diagram 0

    If the parent process has data flowconnecting to a data store, the childdiagram may include the data store as

    well

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-22

    Data Flow Diagram Errors

    The following conditions are errors thatoccur when drawing a data flow

    diagram:A process with only input data flow or

    only output data flow from it

    Add

    New

    Customer

    1

    Add

    New

    Customer

    2

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-23

    Data Flow Diagram Errors

    Data stores or external entities areconnected directly to each other, in anycombination

    Customer D1 Customer

    Vendor D2 Vendor Master

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-25

    Data Flow Diagram Errors

    Omitting data flow from the diagram

    Unbalanced decomposition between a

    parent process and a child diagram

    The data flow in and out of a parentprocess must be present on the child

    diagram

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-26

    Logical Data Flow Diagrams

    Logical data flow diagrams show howthe business operates

    They have processes that would existregardless of the type of systemimplemented

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-27

    Data Flow DiagramProgression

    The progression of creating data flowdiagrams is

    Create a logical DFD of the current systemNext add all the data and processes not in

    the current system which must be presentin the new system

    Finally derive the physical data flowdiagram for the new system

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-28

    Logical Data Flow DiagramsAdvantages

    Advantages of logical DFDs are

    Better communication with users

    More stable systems, since the design isbased on a business framework

    Increased understanding of the business

    by analystsThe system will have increased flexibility

    and be easier to maintain

    Elimination of redundancy

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-30

    Physical Data Flow Diagrams

    Physical data flow diagrams include

    Temporary data stores and transaction files

    Specifying actual document and file names

    Controls to ensure accuracy andcompleteness

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-33

    Triggers and Events

    An input flow from an external entity issometimes called a trigger, since it

    starts activitiesEvents are activities that happen within

    the system

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-35

    Event Tables

    An event table is used to create a dataflow diagram by analyzing each event

    and the data used and produced by theevent

    Every row in an event table represents

    a unique activity and is used to createone process on the data flow diagram

    C d l

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    Kendall & Kendall Copyright 2002 by Prentice Hall, Inc. 9-36

    Use Case and Data FlowDiagrams

    Creating a use case is another approachused to develop a data flow diagram

    A use case