design logic&sistem pengkodean

Sistem Informasi (IF-3171)IF-ITB/MHW/06

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Process Modeling


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Rules Governing DFD (1)• Process :

– No process can have only output– No process can have only input– A process has a verb phrase label

• Data Store :– Data cannot move directly from one data store to

another data store– Data cannot move directly from an outside source

to a data store– Data cannot move directly to an outside sink from

a data store– Data store has a noun phrase label

• Source/Sink :– Data cannot move directly from a source to sink,

its must be moved by a process.


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Rules Governing DFD (2)• Data Flow :

– A data flow has only one direction of flow between symbols

– A fork in a data flow means that exactly the same data goes from a common locations to two or more different processes, data store or source/sink

– A join in a data flow means that exactly the same data come from any of two or more different processes, data store or source/sink to a common locations

– Data cannot go directly back to the same process it leaves

– A data flow to a data store means update (delete or change)

– A data flow from data store means retrieve or use– A data flow has a noun phrase label


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Advanced Rule Governing DFD• A composite data flow on one level can be split

into component data flows at the next level but no new data can be added and all data in the composite must be accounted for in one or more sub flows

• The input must be sufficient to produce the outputs from the process

• At the lowest level of DFD’s new data flow maybe added to represent data that are transmitted under exceptional conditions

• To avoid having data flow lines cross each other


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Four Different Types of DFDs

1. Current physical2. Current logical3. New logical4. New physical


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Guidelines for the drawing DFDs

• Completeness• Consistency• Timing• Iterative development


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DFD creating with Visual-Case• The top-level diagram is called a context

diagram and contains one Functional Transform which represents the entire system.

• The context diagram also shows the external entities that interact with the system.

• The following context diagram shows an order entry system that interacts with customers and shippers.

• The solid lines represent the flow of data.


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DFD creating with Visual-Case

• You can easily show and hide the control transforms and control signals on your diagrams at any time.

• A Control Transform can be decomposed into a State Diagram.

• Together, the state diagram and control transform model the dynamic aspects of the system.


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DFD creating with Visual-Case• Example of a Data Flow Diagram


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Chartist DFD creating• Ex.:


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Logic Modeling


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Deliverables for Logic Modelling• Each process on the lowest (primitive)

level dfd will be represented with one or more of the following :– Structured English representation of process

logic– Decision table representation– Decision tree representation– State transition diagram or table– Sequence diagram– Activity diagram


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Structured English• Modified from of the English language used to

specify the logic of IS processes or the contents of the process boxes in DFD

• Example :READ Quantity-in-stockSELECT CASE

CASE 1 (Quantity stock greater than min order quantity)

DO nothingCASE 2 (Quantity in stock equals min order quantity)

DO nothing


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Decision Table• A matrix representatiom of the logic of adecision,

which specifies the possible conditions for the decision and the resulting actions

• Example :

XProduce Abstain ReportXCalculate overtimeXXXCalculate hourly wage

XPay base salary

>4040<40-Hours workedHHHSEmployee type4321Courses of Action

l e sR uConditions/


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Decision Tree• A graphical representation of a decision

situation point are connected together by arcs and terminate in ovals

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2

Sleep two more hours

Time to get up

sunday

weekday

saturdayyes

no

Sleep one more hour

Go back to sleepLegend :1) Sun up?2) What day is it?


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Criteria for deciding

BestBestThird BestChecking consistency & completeness

BestThird BestBestTransforming conditions & actions into sequence

BestThird BestSecond BestDetermining condition & action

Dec. TreeDec. TableSECriteria


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Conceptual Data Modeling


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Conceptual Data Modeling (CDM)

• CDM is a representation of organization data• Typically do the cdm in parallel with other

requirement analysis & structuring steps during system analysis ( req. determination, req. structuring and alternative generation & selection)

• On the larger system development teams, a subset of the project team concentrates on data modeling while other team member focus attention on process or logic modeling

• Develop/use from prior system dev. a cdm for the current system and build a cdm that supports the scope and req. the proposed or enhanced system


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The Process of CDM

• Begin the process of CDM by developing a CDM for the system being replaced

• Built the CDM that includes all of the data requirements for the new system

• Discovered these requirement from the fact finding methods employed during requirement determination

• One kind of data modeling and database design carried out throughout the system development process


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Relationship Data Modeling and the SDLC

SDLC Phases• Project identification and

selection

• Project Initiation and Planning

• Analysis• Design

• Implementation• Maintenance

Data Modeling Product• Enterprise wide data

model (ER with only entities)

• CDM (ER with only entities for specific project)

• CDM (ER with attributes)• LDM & physical file &

database design

• Database & file definitions

• Data model evolution


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Requirement Determination Question for DM

• What are subjects/objects of business? What type of people, place, things, material, event etc.? (data entities & their description)

• What unique characteristic distinguishes each object from other objects of the same type? (primary key)

• What characteristics describe each object? (attributes and secondary key)

• How do you use this data? ( security control and understanding who really knows the meaning of data)

• Over what period of time are you interested in this data?do you need historical trends, current, estimated or projections? (cardinality & time dimension of data)

• Are all instances of each object the same? Are some object summaries or combination of more detaild object? (supertypes, subtypes & aggregations)

• What events occur that imply associations between various objects? (relationships & their cardinality & degree)

• Is each activity or event always handled the same way or are there special circumstances? (integrity rules, min/max cardinality, time dimension of data)


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Introduction to E-R Modeling


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E-R Data Model• ER Data Model

– is a detailed, logical representation of the entities, associations, and data elements for an organization or for a business area

• ER Diagram is a graphical representation of an ER Model


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Entity• Entities is a person, place, object, event, or concept in the

user environment about which the organization wishes to maintain data.

• Entity type (class/set) is a collection of entities that share common properties or characteristics

• Entity instance is a single occurrence of an entity type

• Naming and defining entity type guidelines :– Singular noun– Descriptive & specific to the organization– Concise– Event entity types (result of the event)


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Attributes & Key• Attribute is a named property or characteristic of an entity that is of

interest to the organization

• Naming & defining attribut guidelines :– Noun– Unique– Each attribute name should follow a standard format

• Candidate key

• Indentifier (primary key)

• Multivalue attributes is an attribute that may take on more than one value for each entity instance

• Repeating group is a set of two or more multivalued attributes that are logically related


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Relationships & Cardinalities• Relationship is an association between the intances of one or

more entity types that is of interest to the organization

• Degree of R (the number of entity types that participate in a relationship) :– Unary R– Binary R– Ternary R

• Cardinalities is the number of instances of entity B that can be (or must) associated with each instance of entity A

• MinMax Cardinalities

• Naming & Defining Relationship guidelines :– Verb phrase– Avoid vague names


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Associative Entity, Subtype & Supertype

• Associative entity is an entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances ( also called a gerund)

• Subtype is a sub grouping of the entities in an entity type that is meaningful to the organization and that share common attributes or relationships distinct from other sub groupings

• Supertype is a generic entity type that has a relationship with one or more subtypes


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Business Rule• Business rule are specifications that preserve the

integrity of a conceptual or logical data model

• Four basic types of business rule are :– Entity integrity, each instance of an entity type must have a

unique identifier that is not null

– Referential integrity constraints, rule concerning the relationship between entity type

– Domains, is the set of all data types and values that an attribute can assume, constraints on valid values for attributes

– Tigering operation, other business rules that protect the validity of attribute values


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Triggering Operations (TO)• TO is an assertion or rule that govern the

validity of data manipulation operations such as insert, update & delete

• TO normally includes the following component :– User Rule, a concise statement of business rule to

be enforced by the triggering operation– Event, the data manipulation operation that

initiates the operation– Entity name, the name of the entity being

accessed and/or modified– Condition, condition that causes the operation to

be triggered– Action, action taken when the operation is

triggered


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Sistem Pengkodean


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CODE• Is a set of rules or principles or laws (especially

written ones) • A coding system used for transmitting messages

requiring brevity or secrecy • Code the pieces with numbers so that you can

identify them later.• In communications, a code is a rule for

converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same sort.


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CODE• In communications and information

processing, encoding is the process by which a source (object) performs this conversion of information into data, which is then sent to a receiver (observer), such as a data processing system.

• In semiotics, the concept of a code is of fundamental importance.

• Interpreting signs requires familiarity with the sets of conventions or codes currently in use to communicate meaning.


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CODE• Source code

– Is the code that a program consists of before the program is being compiled.

– The form in which a computer program is written by the programmer.

– A set of programming language instructions that must be translated to machine instructions before the program can run.

• Object code– Machine-executable instructions, usually generated by a

compiler from source code written in a higher-level language.

– Code in machine-readable form that can be executed by your computer's CPU and operating system, usually linked with libraries to create an executable file.


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CODE• Universal product code

– The standard barcode symbology for retail food packages in the United States.

– A classification for coding data onto products by a series of thick and thin vertical lines.

• bar code– The common term for Universal Product Code.– An array of machine-readable rectangular bars and

spaces arranged in a specific way defined in international standards to represent letters, numbers, and other human-readable symbols.


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CODE• Uniform commercial code

– The State Code which regulates the transfer of and security interests in personal property.

– A set of standard rules, adopted by 49 states, that governs commercial transactions.

• Genetic code– The sequence of nucleotides, coded in triplets

(codons) along the mRNA, that determines the sequence of amino acids in protein synthesis.

– The way in which genetic information is stored in living organisms.


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Pengkodean• Pengkodean dibangun dengan tujuan a.l :

– Memberikan identitas yang ringkas dan unik– Memberikan arti khusus dalam proses

pengolahan– Mereduksi volume data yang harus direkam– Meningkatkan ketelilitian proses pengolahan

• Kode dapat dibangun dari kumpulan karakter :– Numerik– Alfabetik– Alfanumerik– Karakter khusus


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Syarat & Jenis Kode• Dalam merambuat kode ada beberapa hal yang perlu

diperhatikan :– Kemudahan untuk diingat– Harus unik– Fleksibel– Efisien– Konsisten– Panjang sebaiknya sama

• Jenis struktur kode :– Sekuensial– Grup– Blok– Mnemonic


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Kode Sekuensial

Keuntungan Kerugian

Bentuk sederhana Tidak fleksibel Bisa pendek dan unik Tidak punya skema dasar

pengelompokan Mudah dikelola ( bila tidak banyak informasi yang dikelola)

Tidak menunjukkan satu arti untuk item ybs.

Contoh :

001 kursi 002 meja 003 almari 004 rak buku dst.


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Kode BlokKode yang mengklasifikasi item kedalam kelompok/blok tertentu, yang mencerminkan satu klasifikasi tertentu atas dasar pemakaian maksimum yang diharapkan.

Keuntungan Kerugian Nilai kode mempunyai arti

Panjang kode tergantung jml. Blok

Fleksibel, dapat ditambah atau dibuang sebagian

Tidak mudah diingat

Memudahkan proses pelaporan


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Contoh Kode Blok• Contoh :

BLOK KELOMPOK– 1000 – 1999 Ativa lancar– 2000 – 2999 Aktiva tetap– 3000 – 3499 Hutang lancar– 4000 – 4999 Hutang jangka panjang dst.

• Dari blok kode untuk masing-masing kelompok rekeningutama, maka rekening-rekening Aktiva lancar dapatmempunyai kode diantara 1000 s/d 1999 misal sbb.

• Kas– 1100 Piutang dagang

Persediaan produk selesaiPersediaan produk dalam prosesDst.


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Kode Grup

Merupakan kode yang mendasarkan pada field-field dan setiap field mempunyai arti Keuntungan Kerugian Nilai kode mempunyai arti dan dapat menunjukkan hirarki

Kode dapat menjadi panjang

Mudah diperluas Dapat ditambah atau dibuang


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Contoh Kode Grup

• Contoh :NIM : X XX XX XXX

Dimana :- dijit 1 : strata pendidikan- dijit 2,3 : kode program studi- dijit 4,5 : tahun masuk/angkatan- dijit 6,7,8 : no-urut (1 s/d 999)


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Kode Mnemonic• Kode mnemonic digunakan untuk tujuan

supaya mudah diingan denganmenggunakan singkatan atau mengambilsebagian karakter dari item yang akandiwakili kode ini.

• Contoh :– JKT : Jakarta– BDG : Bandung– AMB : Ambon– dst.

design logic&sistem pengkodean

Documents

flow of data

data store data store

data flow diagram

composite data flow

data flow lines

sistem informasi

common locations data

component data flows