Gus_day Blogger

ER-NORMALIZATION

2009-05-03T09:42:00.000-07:00

ER-DIAGRAM:

MAPPING OF ER-DIAGRAM :

NORMALIZATION OF MAPPING :

Pegawai :

Bagian :

Proyek :

Tanggungan :

Kerja :

NORMALIZATION

2009-04-25T02:51:00.000-07:00

Process Design Database

- Gether user need/business
- Develop a needs-based ER Model user/business
- Convert E-R model to the set of relations (tables)
- Normalization to remove the anomaly relations
- Implemented to create a database with a table for each relationship that is normalization

Database normalization

Normalization process is the establishment of the database structure so that most of the ambiguity can be removed. Normalization stage, starting from the most mild (1NF) to most stringent (5NF). Usually only up to the level of 3NF or BCNF because already sufficient to generate the table-table good quality.

Why do normalization?
- Optimizing table structures
- Increase speed
- The income data is the same
- More efficient in the use of storage media
- Reduce redundancy
- Avoid anomalies (insertion anomalies, deletion anomalies, update anomalies)
- Improved data integrity

A table saying good (efficient) or if the normal 3 to meet the following criteria :
- If there is decomposition (decomposition) table, it must be guaranteed safe dekomposisinya (Lossless-Join Decomposition). That is, after the table is described / didekomposisi a new table-table, the table-table can generate a new table with the same exact.
- Maintain dependence on the functional changes in data (Dependency preservation)
- Does not violate Boyce-Code Normal Form (BCNF)

If the three criteria (BCNF) can not be met, then at least the table does not violate the Normal Form of the third stage (3rd Normal Form / 3NF)

Functional Dependency

Functional Dependency describes a relationship attributes in relation. An attribute said functionally dependant on the other, if we use the value attribute to determine the value of other attributes. Symbol that is used to represent the functional dependency that is readable in determining functional.

Notation : A --> B
A and B are attributes of a table. A means of determining the functional B or B depends on A, if and only if there are 2 rows of data with the same value of A, then B is also the same value.

Notation : A --> B or A x --> B
It is the opposite of the previous notation.

FUNCTIONAL DEPENDENCY (FD)

Functional Dependency
NRP --> Nama
Mata_Kuliah, NRP --> Nilai

Non Functional Dependency
Mata_Kuliah --> NRP
NRP --> Nilai

Functional Dependency of the table value
- NRP --> Nama
Karena untuk setiap nilai Nrp yang sama, maka nilai Nama juga sama.
- {Mata_kuliah, NRP} --> Nilai
Because the value of attributes depending on the NRP and Mata_kuliah together. In another sense Mata_kuliah for the NRP and the same, they also rated the same, because Mata_kuliah and the NRP is a key (a unique).
- Mata_kuliah --> NRP
- NRP --> Nilai

FIRST NORMAL FORM – 1NF

A table on the form said to be normal if I did not reside in the unnormalized form of a table, where there is a kind of field multiplication and field that allows a null (empty).

Not allowed the:
- Many attributes of value (Multivalued attributes).
- Attributes composite or a combination of both.

So the price should be the domain attribute price atomic

Ex Student Data as follows:

Or:

The table above does not meet the requirements 1NF

Example :

Dekomposisi menjadi :
- Table Student

- Table Hobby

SECOND NORMAL FORM

Normal form 2NF met in a table if it meets the form of 1NF, and all the attributes than the primary key, have a full Functional Dependency on primary key. A table does not meet 2NF, if there are attributes that ketergantungannya (Functional Dependency) are only partial (only depending on the part of the primary key). If there are attributes that have no dependence on the primary key, then the attributes must be moved or removed. Y is full if it is said to delete an attribute A from X means that Y is no longer dependent functional --> Functional dependency X. Y said if deleting a partial attribute A from X means that Y is functionally dependent --> Functional dependency X. Relation scheme R in the form 2NF if every non-primary key attribute A element R depends on the full primary key fungsioanl R.

Example :

The following table meet 1NF, including but not 2NF

Does not meet 2NF, because (NIM, KodeMk) is regarded as the primary key:
{NIM, KodeMk} --> NamaMhs
{NIM, KodeMk} --> Alamat
{NIM, KodeMk} --> Matakuliah
{NIM, KodeMk} --> Sks
{NIM, KodeMk} --> NilaiHuruf

Table needs to be some table decomposition eligible 2NF

Functional dependency:
- {NIM, KodeMk} --> NilaiHuruf (fd1)
- NIM --> {NamaMhs, Alamat} (fd2)
- KodeMk --> {Matakuliah, Sks} (fd3)

So:
- fd1 (NIM, KodeMk, NilaiHuruf) --> Tabel Nilai
- fd2 (NIM, NamaMhs, Alamat) --> Tabel Mahasiswa
- fd3 (KodeMk, Matakuliah, Sks) --> Tabel MataKuliah

THIRD NORMAL FORM – 3NF

Normal form 3NF fulfilled if the form meets 2NF, and if there are no non-primary key attribute that has a dependence on non-primary key attributes of the other (transitive dependencies).

Example :

Table following students eligible 2NF, 3NF, but does not meet :

Because there are non-primary key attribute (ie, City and Provincial), which has a dependence on non-primary key attributes of the other (is KodePos):
KodePos --> {Kota, Provinsi}

So that the table should be decomposition :
Students (NIM, NamaMhs, Jalan, KodePos)
- KodePos (KodePos, Provinsi, Kota)

Boyce-Codd Normal Form (BNCF)

Boyce-Codd Normal Form constraint has a stronger form of the Normal third. To be BNCF, relations must be in the form of Normal Kesatu and forced each of the attributes depends on the function in the super key attributes.

In the example below there is a relationship seminar, is the Primary Key NPM + Seminar.
Students may take one or two seminars. Each seminar requires 2 each of the students and led by one of the 2 seminar. Each leader can only take one seminar course. NPM in this example indicates a seminar and teacher.

Relations Seminar is a form of Third Normal, but not BCNF
Seminar Code because the function depends on the Pembimbing, if any Pembimbing can only teach a seminar. Seminar depend on one key attribute is not as super disayaratakan by BCNF.

Normal Form Of The Fourth And Fifth

Relations in the fourth normal form (NF 4) if the relation in BCNF and dependency tdak contain many values. To remove the dependency of many values from a relation, we divide the relationship into two new relations. Each relation contains two attributes that have a lot of relationship value. Relations in fifth normal form (5NF) deal with the property called the join without any loss of information (lossless join). Fifth normal form (also called the 5 NF PJNF (projection join normal form). The case is very rare and appear difficult to detect in practice.

DATABASE & ER-DIAGRAM

2009-04-18T09:35:00.000-07:00

Definition of Database

Database is a set of data stored in the magnetic disc, optical disc, or other secondary storage. Integrated collection of related data from an enterprise (companies, goverment agecies or private).
- Manufacturing company : production planning data, actual production data, data ordering materials, etc.
- Hospital : patient data, doctor, nurse, etc.

Database Management System

- Collection/database combined with software applications that are based database.
- This application program used to access and maintain database.
- The main purpose DBMS (Database Management System) is to provide an environment that is efficient and easy to use, withdrawal and storage of data and information.

Bit, Byte, Field

- Bit is the smallest pieces of data that contains the value 0 or 1.
- Byte is a collection of bits-a bit like.
- Field is a set of byte-byte similar, in the database used the term attribute.

Attribute/Field

Attribute is the nature or characteristics of an entity that provides provide detail on these entities. A relationship can also have attributes.
Sample attributes :
- STUDENTS : NIM, NAME, ADDRESS
- CAR : PLAT_NUMBER, COLOR, TYPE, CC

Type Attribute

Single vs Multivalue
- Single typically can only be filled at most one value.
- Multivalue can be filled with more than one value with the same type of.
Atomic vs Composition
- Atomic can not be divided into the attributes of smaller.
- The composition is a combination of several attributes of a smaller.
Devired Attribute
Attribute value can be derived from other attribute values, Suppose that the age attribute of the date of birth.
Null Value Attribute
Attributes that have no value to a record
Mandatory Value Attribute
Attributes must have values

Record/Tuple

It is a line of data in a relationship, and consists of a set of attributes where the attribute is to inform each other entity/relationship fully.

Entity/File

File is a collection of records, and similar elements have the same, same but different attribute data value.

File Type :
In processing applications, files can be categorized as follows:
- Master File
- Transaction File
- File Report
- File History
- File Protection
- File Work

Domain

Domain is the set of values that are allowed to reside in one or more attributes. Each attribute in a database relational is defined as a domain.

Element Key Data

Key elements of record which is used to find these records at the time of access, or can also be used to identify each entity/record/line.

Species of Key

Superkey is one or more attributes of a table that can be used to identify entityty/record of the table are unique (not all attributes can be superkey).
Cadidate Key is a super key with minimal attributes. Candidate must not contain a key attribute of the table so that the other candidate key is certain superkey but not necessarily vice versa.

Primary Key
One of the key attributes of the candidate can be selected / specified a primary key with the three following criteria:
1. Key is more natural to use as reference.
2. Key is more simple.

Alternate Key is an attribute of the candidate key is not selected to be primary key.
Foreign Key is any attribute that points to the primary key in another table. Foreign key will be going on a relationship that has kardinalitas one to many (one to many) or many to many (many to many). Foreign key is usually always put on the table that lead to many.
External Key is a lexical attribute (or set of lexical attributes) that values are always identify an object instance.

ERD (Entity Relationship Diagram)

ERD (Entity Relationship Diagram) is a model of a network that uses word order is stored in the system of abstract.

Differences between the DFD (Data Flow Diagram) and ERD (Entitiy Relationship Diagram).
- DFD (Data Flow Diagram) is a model of network functions that will be implemented by the system.
- ERD (Entitiy Relationship Diagram) is a model that emphasizes the network data on the structure and relationship data.

Elements of the ERD (Entitiy Relationship Diagram)

- Entity
In the ER Diagram Entity is described with the form of a rectangle. Rntity is something that exists in the real system and the abstract where the data stored or where the data.

- Relationship
ER diagram on the relationship can be described with a lozenge. Relationship is a natural relationship that occurs between entities. In general, the name given to the verb base making it easier to do readings relations.

- Relationship Degree
Is the number of entities participating in a relationship. Degree which is often used in the ERD (Entitiy Relationship Diagram).

- Attribute
Is the nature or characteristics of each entity and relationship.

- Cardinalitation
Tupel indicates the maximum number that can be relationships with entities on the other entity.

Degree of Relationship

- Unary Relationship is the relationship model between the entity originating from the same entity set.
- Binary Relationship is a relationship model between 2 entities.
- Ternary Relationship is a relationship between the instance of 3 types of entities are unilateral.

Cardinalitation

There are 3 kardinalitas relations, namely:
- One to One : Level one to one relationship with the one stated in the entity's first event, only had one relationship with one incident in which the two entities and vice versa.
- One to Many or Many to One : Level one to many relationship is the same as the one to many depending on the direction from which the relationship views. For an incident on the first entity can have any relationship with banyaj incident on the second entity, if the one incident in which two entities can only have one connection with incident on the first entity.
- Many to Many : If any incident occurs in an entity many have relationships with other entities in the event.

DATA FLOW DIAGRAM (DFD)

2009-04-04T19:04:00.002-07:00

Data Flow Diagram

Describe the system distribution in the small module. Make easy use less realize the computer area for an understand system to worked.

Context Diagram

Consist of one process and describe the scop from any system. And then is a high level from the Data Flow Diagram to describe all input to the system and output from the system. The context diagram usually limitted by Boundary. And then not to be any storage.

Zero Diagram

Describe the process from the Data Flow Diagram. Give opinion according to comprehensive hit the system to handled, show the fuction or important system exiting, data flow and external entity. In this level maked existence the data storage. For the process not be detailed againt in the next level so to added the symbol ‘*’ or ‘P’ in the end of process number. Balancing of the input and output between zero diagram with context diagram must to take care.

Detail of Diagram

That is a diagram to decomposing the process what is there in the zero diagram or on the level.

Level numberizatio in the Data Flow Diagram:
- Level name is 0, diagram name is context, and there is not the number of process.
- Level name is 1, diagram neme is 0 (zero) diagram, and the number of process is 1.0, 2.0, 3.0, etc.
- Level name is 2, diagram name is 1.0, and the number of process is 1.1, 1.2, 1.3, etc.
- Level name is 3, diagram name is 1.1, and the number of process is 1.1.1, 1.1.2, etc.

In the one level must be not found more from 7 process and maximal is 9, when be more so must done decomposition.

Process Spesification

Every process in the Data Flow Diagram must heving the process spesification. In the top level method to used for describe the process can by using descriptive sentence. In the level to more detail is in the most under process (functional primitive) need the more structured spesification. Process spesification will be guide for programer in the make the program (coding). Method to used in the process spesification is process explanation in the form of story, decision table, and decision tree.

Unitary Outside

Certain beyond the system, but he give the data to in the system or give the data from the system. Usually symbolized with notation box. External entity not to belong part from system. Nomenclature is :
- The terminal name is shaped noun.
- The terminal can be not have same the name except the object really same.

Data Current

Data current is a place currences information. Described with straight line tto connect the component from the system. Data current showed by arrow direction and the line given the name on data current to flow. Data current to flow in the process, data storage and to show the data current from data to shaped the input for system. Guide the gift of the name is :
- Name of data flow consist of many word flow to connected with line continues.
- There may not be any data flow it’s the same of the name and gived the name must to reflect the contents.
- Data flow consist of many element can to asked with element group.
- Avoid to use any word is ‘data’ and ‘information’ for give the name in the data flow.
- The name of flow can be to written complete.

Rule other:
- Name data flow to come in a process not to be same by name of data flow to out from the process.
- Data flow to come in or out from the data storage can be not given the name when :
a. The simple of data flow and easy understood.
b. Data flow to describe all data item.
- There may not be any data flow from terminal to data storage or on the contrary because the terminal not a part from system, the connection of the terminal by data storage must pass the process.

Process

Process is a what to working by system. Process can to cultivate the data or data flow come to be out of data flow. The function of process is transformation the one or many input data be one or many output data appropriated with spesification to desirable. Any process have a one or many input and produce one or many output. The process often also called as bubble.

Guide the gift of the name process is :
- Name of process consist of many verb and noun to reflect function of the process.
- Don’t use process word as part from name a bubble.
- There may not be any process to have the same of the name.
- The process must given the number. Sequence the number can be to follow the flow or sequence the process, but such be sequence the number meaningless absolutely is the sequence of process according to chronological.

Data Storage

Data storage is a data repository in the system. Symbolized with a pair parallel line or two line with one of the side opened. The process can be take the data from or give the data to datebase. Guide the gift of the name is :
- The name must be reflect the data storage
- When the name be more from one word so must to take sign continues

Data Dictionary

The function of data dictionary to help a system user for interprate the aplication to detail and to unite all data element to used the system be exacttly so that user and system analyst have a same base explanation about input, output, storage, and process. In analysis stage, data dictionary to use as a communication tools that is analys system with user. In system planning stage, data dictionary to use for plan the input, report, and database. Data current in the Data Flow Diagram has global, more detail of explanation can be look in the data dictionary.

Data dictionary hold matter as follow is :
- Name of data current : must be registerred so that reader need a furthe more explanation about of a data current can be find so easy.
- Data form : to use for unite the data dictionary to use timer the system planning.
- Data current : show whence a data to flow and where a data to go.
- Explanation : give explanation about meaning from data current.

Balancing in the Data Flow Diagram

Data flow to come in and out from one process must be same with data flow to come in and out from detail of process in the level or stage under. Name of data flow come in and out from one process must be same with name of data flow to come in and out from detail of the process. Total and outside of entitas name a process must be same with total and outside of entitas name from detail of the process. Matter that must be played a Data Flow Diagram to have more one level is :
- Must found balancing input and output the one level and other level.
- Balancing the 0 level and 1 level can be look in the input or output from data flow to and or from terminal in the 0 level, while be balancing the 1 level and 2 level can be look in the input or output from data flow to or from process cornerned.
- Name of data flow, data storage, and terminal in the every level must be same if same object.

Prohibition in the Data Flow Diagram

- Data current can be not from direct outside of entitas to go to other outside of entitas without pass a process.
- Data current can be not from direct data saving to go to outside of entitas without pass a process.
- Data current can be not from direct data saving to go to other data saving without pass a process.
- Data currrent from one direct process to go to other process to pass a data saving can be may a void.

Beginning Observation, Requirement Analysis

2009-03-28T06:30:00.000-07:00

Concept Investigation System

1. Difference of between the target of system and conditon of system actually.
2. The problem detection the report is not real true:
- Purpose too ideal
- Deficit the resource and attitude.
- Measurement the system less accurate.
- Purpose of the system that lag.
- Difference between ideal system and temporary system
3. Problem Solving
- The Spelling of system was out that is walking  the investigation in detail.
- Get the ideal system consensus.
- Develop the several alternative.
- Choose the best alternative.
4. Purpose the investigation
- Show the problem actually happen

Obstacle in the Investigation System

In the investigation, many obstacle can be to appear:
- Time
- Cost
- Science
- Policies
- Mix hand

Recomendation

The result of investigation is a recomendation containing about:
- Doesn’t take the step to whatever  not found the problem
- The system maintenance  small problem
- Increase ability or user craft
- Considering the system modification according to total
- Laid the problem that happened in to the paln of system development can be done

Tactics of Investigation

1. Why need the tactics?
- Find all problem
- Detect the appearance problem
- Determine the corret solution
2. Be done so that all system elements can get solution tender without disturb their activity.
3. Some tactics can be conducted:
- Listen the opinion from system executant
- Don’t give begining solution
- Compare the story from the system executant toward the same of the case
- Look at the problem of inkonsistensi logikal
4. Direct:
- Kuesioner
- Question and answare
- Observation
5. Not direct:
- Procedure current
- Study the document
- Sample
- Tabular

Description of System in this time

- Input
- Output
- Files
- Data Elements
- Transaction volume and action of document
- Data flow chart

Requirement Analys

Intensive interaction phase between system analys by with and user where team of system development show it’s membership to get the response and wearer belived so that get the good participation.

1. Four target want to achieved:
- Explain the system to entirety
- Describe the system information to ideal
- Bring the ideal of system information to the condition this time with attention the obstacle of resource
- Give push to confidence the user in the system development

2. Method
- Question and answer
- Kuesioner
- Observation
- Analys procedure
- Document observation

3. Obstacle of resource
- Time
- Money
- Skill
- Technology
- External factor

4. Document need the analys
- Analys directive : the connection with user ends, process observation, troubleshoot in data collecting
- Requirement user : requirement actually, requirement report, requirement training, and influence the old system
- System obstacle : explain the time and cost obstacle, skill, technology, and external factor.
- Document shaped the instrument of data collecting, statistics consensus, data current according to logikal and physical, the first data element in the data dictionary

Generating Systems Alternatives

How does manner nearing the condition of system in this time with the ideal system condition?
- Make the alternative for break the problem of system information
- The best alternative can be appliened wisely

Strategy choice:
- Distributed versus centralized processing
Change the information decision from centralized data processing to decentralized end user responsibility center.
- Integrated versus dispersed database
Planning the system must considering the data everything that come in the data base and come in the file.
- Surround Strategy of System Development
Around of environment important strategy in the expropriation matter the company because the system information from company other may be differ with company in this time.

Tactics choice
Done before choice the operational planning.

Choice the operational planning
Planning can be grouped in to:
- Input
a. Online Vs Off Line Data Entry
b. Keyed Vs Machine Readable Data Entry
c. Centralized Vs Decentralized Data Entry
- Processing
a. Batch Vs Realtime record update
b. Sequential Vs Direct Access to records
c. Single Vs Multiple User update of records
- Output
a. Traditional Vs Turn Around Documents
b. Structured Vs Inquiry based reports

Selecting The Proper System

Tactics compares : the system compared based on cost and profit according to relative. There 3 manners A system said superiorer with other system if:
- A have a cost lower from in B and the profit both same
- A have a cost lower from in B and A produce profit more than B
- A and B have same the cost but profit that produced a more many

Many method of System Comparation:
- Break Even point Analyisis
- Payback Period
- Discounted PayBack period
- Internal Rate of Return

Cost category:
- Hardware
- Software
- People
- Suppliers
- Teleccommunications
- Physical sites

Cost details
Compare the cost of system information pass system life, the analys of how much expense change for the future and there is 3 model of expanse information system that is a linear, exponential and step function.

Cost of system information can be happen once and can be happen according to chronically.
- Cost of system information that happened once is ontime cost and development cost happened at system development.
- Cost of system information that happened continually among other things is reccuring cost also operational cost of where this expense is happened by the moment of information system operate every day.

Factor of System Information

Qualitative factor instructing good information of system performance
- Decrease error level
- Decrease time to repair error
- Decrease time listen carefully from workstation alternative
- Quickening ready time of information
- Improving system security
- Multiply to update the active source record
- Improving wearer satisfaction

Factor of company strategy
- Consumer satisfaction
- Sale level increases
- Consumer commitment and vendor
- Information of product marketing

Presenting System Study

- Conducting presentation in a word
- Lessening technique clarification in detail
- Presenting clearly with the visual assistive appliance
- If using model use the assistive appliance for example laptop so that more informative
- Emphasizing advantage from proposal of information system with a few existing alternative according to natural by condition of company

Decision Continue or Not

- If company set mind on to develop the system hence information department will do the process hereinafter that is Process the Desain System
- If on the contrary hence System Development Life Cycle ( SDLC) will be discontinued
- Frequently will be found problem with the study system and and usually top management will ask conducting of reworking to study system
- Model will explain the some part of step repeated and sometime information department will make decision to repeat the step of before explaining study system
- With the alternative, decision to repeat a not to speak of or previous step SDLC of Go – No – Go Decision

Tinjauan Umum Pengembangan Sistem

2009-03-07T04:33:00.000-08:00

1. Pentingnya Pengembangan Sistem Informasi

a. Adanya permasalahan – permasalahan (problem) yang timbul di sistem yang lama. Permasalahan yang timbul dapat berupa:

- Kecurangan – kecurangan disengaja yang menyebabkan tidak amannya harta kekayaan perusahaan dan kebenaran dari data menjadi kurang terjamin.

- Kesalahan – kesalahan yang tidak disengaja yang juga dapat menyebabkan kebenaran dari data kurang terjamin.

- Tidak efisiennya operasi.

- Tidak ditaatinya kebijaksanaan manajemen yang telah ditetapkan.

b. Pertumbuhan Organisasi yang menyebabkan harus disusunnya sistem yang baru. Pertumbuhan organisasi diantaranya adalah kebutuhan informasi yang semakin luas, volume pengolahan data semakin meningkat, perubahan prinsip akuntansi yang baru. Karena adanya perubahan ini, maka menyebabkan sistem yang lama tidak efektif lagi, sehingga sistem yang lama sudah tidak dapat memenuhi lagi kebutuhan informasi yang dibutuhkan manajemen.

c. Untuk meraih kesempatan – kesempatan (oppotunities).

Teknologi informasi telah berkembang dengan cepat. Teknologi informasi telah berkembang dengan cepat. Perangkat keras komputer, perangkat lunak, dan teknologi komunikasi telah begitu cepat berkembang. Organisasi mulai merasakan bahwa teknologi informasi ini perlu digunakan untuk meningkatkan penyediaan informasi sehingga dapat mendukung dalam proses pengambilan keputusan yang akan dilakukan oleh manajemen.

d. Adanya instruksi – instruksi (directives)

Penyusunan sistem yang baru dapat juga terjadi karena adanya instruksi – instruksi dari atas pimpinan ataupun dari luar organisasi seperti misalnya peraturan pemerintah.

2. Tujuan Pengembangan Sistem Informasi

- Memecahkan permasalahan – permasalahan

- Meraih kesempatan – kesempatan

- Memenuhi instruksi yang diberikan

3. Harapan Informasi Setelah Menerapkan Sistem Informasi

a. Performance (Kinerja)

- Diukur menggunakan throughput dan response time

b. Information (Informasi)

- Peningkatan kualitas informasi

c. Economy (Ekonomis)

- Peningkataan manfaat vs penurunan biaya

d. Control (Pengendalian)

- Mendeteksi dan memperbaiki kesalahan

e. Efficiency (Efisiensi)

- Efisien operasional

f. Services (Pelayanan)

- Peningkatan pelayanan sistem

4. Prinsip Pengembangan Sistem Informasi

a. Sistem yang dikembangkan adalah untuk manajemen.

b. Sistem yang dikembangkan adalah investasi modal yang besar.

c. Sistem yang dikembangkan memerlukan orang yang terdidik.

d. Tahapan kerja dan tugas – tugas yang harus dilakukan dalam proses pengembangan sistem.

e. Proses pengembangan sistem tidak harus urut.

f. Jangan tekut membatalkan proyek.

g. Dokumentasi harus ada untuk pedoman dalam pengembangan sistem.

5. Pengembangan Sistem Life Cycle Models

a. Model Waterfall

Pada model ini dilakukan dengan proses tahap demi tahap yang dilalui harus menunggu selesainya tahap sebelumnya dan berjalan berurutan. Sebagai contoh tahap desain harus menunggu selesainya tahap sebelumnya yaitu tahap requipment. Secara umum tahapan pada model waterfall dapat dilihat pada gambar berikut:

Pressman memecah model ini menjadi enam tahapan meskipun secara garis besar sama dengan tahapan – tahapan model waterfall pada umumnya. Berikut adalah penjelasan dari tahap – tahap yang dilakukan dalam model ini menurut pressman:

- Sistem/Information Engineering and Modeling

Pemodelan ini diawali dengan mencari kebutuhan dari keseluruhan system yang akan diaplikasikan dalam bentuk software.

- Software Requipments Analysis

Proses pencarian kebutuhan diintesifkan dan difokuskan pada software. Untuk mengetahui sifat program yang akan dibuat maka pada software engineer harus mengerti tentang domain informasi dari software, misalnya fungsi yang dibutuhkan, user interface. Dari dua aktifitas tersebut harus didokumentasikan dan ditunjukkan pada pelanggan.

- Design

Proses ini digunakan untuk mengubah kebutuhan-kebutuhan diatas menjadi representasi ke dalam bentuk “blueprint” software sebelum coding dimulai. Desain harus dapat mengimplementasikan kebutuhan yang telah disebutkan pada tahap sebelumnya. Seperti 2 aktivitas sebelumnya, maka proses ini juga harus didokumentasikan sebagai konfigurasi dari software.

- Coding

Untuk dapat dimengerti oleh mesin, dalam hal ini adalah komputer, maka desain tadi harus diubah bentuknya menjadi bentuk yang dapat dimengerti oleh mesin, yaitu ke dalam bahasa pemrograman melalui proses coding. Tahap ini merupakan implementasi dari tahap design yang secara teknis nantinya dikerjakan oleh programmer.

- Testing/Verification

Sesuatu yang dibuat haruslah diujicobakan. Demikian juga dengan software. Semua fungsi-fungsi software harus diujicobakan, agar software bebas dari error, dan hasilnya harus benar-benar sesuai dengan kebutuhan yang sudah didefinisikan sebelumnya.

- Maintenance

Pemeliharaan suatu software diperlukan, termasuk di dalamnya adalah pengembangan, karena software yang dibuat tidak selamanya hanya seperti itu. Ketika dijalankan mungkin saja masih ada errors kecil yang tidak ditemukan sebelumnya, atau ada penambahan fitur-fitur yang belum ada pada software tersebut. Pengembangan diperlukan ketika adanya perubahan dari eksternal perusahaan seperti ketika ada pergantian sistem operasi, atau perangkat lainnya.

Sumber :

http://hansiaditya.wordpress.com/2007/09/25/waterfall-process-model/

b. Model Iteratif

Model inkremental menggabungkan elemen-elemen model waterfall (diaplikasikan secara berulang) dengan prototipe iteratif. Model ini memakai urutan-urutan linier dalam model seiring dengan laju waktu. Setiap urutan linier menghasilkan pertambahan perangkat lunak. Pada saat model pertambahan dipergunakan, pertambahan pertama seringkali adalah produk inti. Produk inti ini kemudian dipergunakan oleh pelanggan. Sebagai hasil dari pemakaian dan/atau evaluasi, prototipe dikembangkan untuk pertambahan selanjutnya. Prototipe tersebut menekankan modifikasi produk inti agar dapat memenuhi kebutuhan pelanggan dan fitur serta fungsionalitas tambahan. Model inkremental ini seperti model prototipe dan pendekatan-pendekatan evolusioner lain yang bersifat iteratif. Tetapi tidak seperti model prototipe, model inkremental berfokus pada penyampaian produk operasional dalam setiap pertambahannya. Pertambahan awal ada di versi striped down dari produk akhir, tetapi memberikan kemampuan untuk melayani pemakai dan juga menyediakan platform untuk evaluasi oleh pemakai. Perkembangan incremental berguna pada saat staffing tidak dapat digunakan untuk batas waktu bisnis yang telah ditetapkan untuk proyek tersebut. Jika produk inti diterima, maka staf tambahan bisa ditambahkan untuk mengimplementasikan pertambahan selanjutnya.

c. Model Spiral

Merupakan model proses perangkat lunak evolusioner yang merangkai sifat iterative dari prototype dengan cara control dan aspek sistematis model sequensial linier.

Tahapan – tahapan model spiral :

- Komunikasi Pelanggan, merupakan tugas – tugas untuk membangun komunikasi antara pelanggan dan kebutuhan – kebutuhan yang idiinginkan oleh pelanggan.

- Perencanaan, merupakan tugas – tugas untuk mendefinisikan sumber daya, ketepatan waktu dan proyek informasi lain yang berhubungan.

- Analisis Resiko, merupakan tugas yang dibutuhkan untuk menaksir resiko manajemen dan teknis.

- Perekayasaan, merupakan tugas yang dibuthkan untuk membangun satu atau lebih representasi dari aplikasi tersebut.

- Konstruksi dan peluncuran, merupakan tugas – tugas yang dibutuhkan untuk mengkontruksi, menguji, memasang, dan memberi pelayanan kepada pemakai.

6. Pendekatan Dari Pengembangan Sistem

Terdapat beberapa pendekatan untuk mengembangkan sistem, yaitu sebagai berikut :

a. Pendekatan klasik lawan pendekatan terstruktur

- Pendekatan klasik

Tahapan – tahapan dalam SDLC. Tidak mengikutsertakan pengguna, lebih menekankan analis sistem.

- Pendekatan terstruktur

Pengguna terlibat dari awal untuk menentukan kebutuhan sistem. Menggunakan tools – tools seperti data flow diagram.

b. Pendekatan sepotong lawan pendekatan sistem

- Pendekatan sepotong

Menekankan pada suatu aplikasi atau kegiatan. Tidak mengindahkan sasaran keseluruhan.

- Pendekatan sistem

Melihat sistem sebagai satu kesatuan yang utuh. Menekankan pada pencapaian sasaran secara keseluruhan.

c. Pendekatan bawah-naik lawan pendekatan atas-turun

- Pendekatan bawah-naik

Dimulai dari level bawah yaitu operasional. Merupakan ciri – ciri pendekatan klasik. Dikenal dengan istilah data analysis.

- Pendekatan atas-turun

Dimulali dari level atas yaitu perencanaan strategi. Merupakan ciri – ciri pendekatan terstruktur. Dikenal juga dengan decision analysis.

d. Pendekatan sistem-menyeluruh lawan pendekatan moduler

- Pendekatan sistem-seluruh

Mengembangkan sistem secara serentak dan menyeluruh dan merupakan ciri – ciri pendekatan klasik.

- Pendekatan moduler

Memecahkan sistem yang rumit menjadi bagian – bagian yang sederhana. Sistem yang dikembangkan menjadi tepat waktu, mudah untuk dipahami, dan dipelihara. Merupakan ciri – ciri pendekatan terstruktur.

e. Pendekatan lompatan jauh lawan pendekatan berkembang

- Pendekatan lompatan jauh lawan

Mengembangkan sistem secara serentak menggunakan teknologi canggih. Beresiko tinggi dan menghabiskan banyak biaya.

- Pendekatan berkembang

Menerapkan teknologi canggih untuk aplikasi – aplikasi tertentu. Dikembangkan untuk mengikuti kebutuhan. Hemat biaya dan dapat mengikuti perkembangan teknologi.

7. Arti Dari Metodelogi, Metode, dan Algoritma

- Metodelogi merupakan metode – metode digunakan oleh suatu ilmu pengetahuan.

- Metode merupakan suatu cara sistematik untuk mengerjakan sesuatu.

- Algoritma merupakan urut – urutan prosedur untuk memecahkan suatu masalah

8. Tiga Klasifikasi Metodelogi Pengembangan

a. Functional decomposition methodologies.

Metodelogi ini menekankan pada pemecahan dari sistem kedalam subsistem – subsistem yang lebih kecil, sehingga akan lebih mudah untuk dipahami, dirancang dan diterapkan.

b. Data-oriented methodologies.

Metodelogi ini menekankan pada kearakteristik dari data yang akan diproses. Metodelogi ini dapat dikelompokkan menjadi dua kelas, yaitu:

- Data-flow oriented methodologies.

Metodelogi ini secara umum didasarkan pada pemecahan dari sistem kedalam modul – modul berdasarkan dari tipe elemen data dan tingkah laku logika modul tersebut didalam sistem. Dengan metodelogi ini, sistem secara logika dapat digambarkan secara logika dari arus data dan hubungan antar fungsinya didalam modul – modul di sistem.

- Data structure oriented methodologies.

Metodelogi ini menekankan struktur dari input dan output di sistem. Struktur ini kemudian akan digunakan sebagai dasar struktur dari sistemnya. Hubungan fungsi antar modul atau elemen – elemen sistem kemudian dijelaskan dari struktur sistemnya.

c. Prescriptive Methodologies.

Biasanya disediakan oleh pabrik pembuat perangkat lunak.

9. Teknik Penggunaan Dalam Pengembangan Sistem

a. Teknik manajemen proyek, yaitu CPM (Critical Path Method) dan PERT (Program Evaluation and Review Technique). Teknik ini digunakan untuk penjadualan proyek.

b. Teknik menemukan fakta (Fact finding techniques), yaitu teknik yang dapat digunakan untuk mengumpulkan data dan menemukan fakta – fakta dalam kegiatan mempelajari sistem yang ada. Teknik – teknik diantaranya adalah:

- Wawancara (interview)

- Observasi (Observation)

- Daftar pertanyaan (questionaires)

- Pengumpulan sample (sampling)

c. Teknik analisis biaya/mafaat (cost-effectiveness analysis dan cost-benefit analysis).

d. Teknik untuk menjalankan rapat.

e. Teknik inspeksi/walkthrough.

10. Perbedaan antara Analis Sistem dan Pemrogram.

- Analis Sistem adalah mempelajari masalah – masalah dan menentukan kebutuhan pemakai sistem untuk mengidentifikasikan pemecahan.

- Pemrogram adalah menulis kode program berdasarkan rancang bangun yang dibuat oleh analis.

Basic Concept of Information System Analysis and Design

2009-02-20T01:40:00.000-08:00

Before studying what that Information Systems Analysis and Design, first we have to know what that system and what that information.

WHAT IS SYSTEM?

There are two approaching to definition of system:

1. Definition of system based on approach of procedure

According to this approach, system interpreted by as a working network from procedures which is interaction and work along to finish a specific-purpose or goal. A procedure is a correct sequences of instruction steps explaining what have to be done, who have to do, when have to be done and how to do that.

2. Definition of system based on approach of element

According to this approach the definition of system is a set of elements which is have interaction to reach specific-purpose or goal.

CHARACTERISTIC OF SYSTEM

Characteristic a system can be explained as follows:

1. Components

Consist of a number of components which interact, what each other working along to form an unity. The example is Supra System that is a larger ones system.

2. Boundary

A system has a boundary to limiting system with environmental or other system outside its.

3. Environments

Environment is a media link between a subsystem with other subsystem.

4. Input

Entered energy into system can in the form of treatment input and signal input. The treatment input is entered energy system to can walk. While signal input is energy which in process to yield output.

5. Output

The result from processed energy and classified is become an output which good for and rest of dismissal.

6. Process

Process is the change an input become output.

7. Target (objective)/goal

Otherwise have the target then system operation there will be no utilizing of. The system is told succeed if it has reach the target/its goal.

The Classification Of System
a. Deterministic System
The Certain system operate with behaviour which have earned can be predicted, interaction between its sharess can be detected categorically so that its output can be forecasted. for example of : Computer programe, executing precisely as according to its instruction network. System of pay, and others.
b. Probabilistic System
The System which is input and its process can be defined, but yielded output cannot be determined categorically; ( always there is a little mistake / deviation to forecast of the way system). for Example : marketing system)
c. Open System
The system that relation and effect external environment .This system accept input and yield output for external environment / the other sub system, so that have good operation system. This system tend to measure up to adaptation, can adapt to its environment so that can continue its.
d. Closed System
The System Physical where the process that happened do not experience of transfer of items, information or energy with environment outside system. This system work automatically without existence of interfere in of external side of it.
e. Relatively Closed System
The closed System but doesn't closed at all to accept other influences. This system in its operation can accept influence from outside which have been defined in certain boundarys.
f. Artificial System
The System imitating occurence in system. This system is formed pursuant to occurence in nature where human being unable to do it. Equally imitat exist in nature.
g. Natural System
The natural System is occurence in nature. for Example of : sea, solar system and others.
h. Manned System
The System explanations of behaviour covering human being taking part in. This system can be depicted in way of as follows:
The System of Human being focus the relations between human being
The System of Human being - Machine, System which involve machine to a target
The Machine System, automatic system where human being have duty to start and finish system, meanwhile human being entangled also to monitor system.

Information
Data is fact. Information is data that processed become better form and more meaning to accept it. If data is not useful to accept it so the data cannot be referred as by information.

QUALITY OF INFORMATION

To get information with quality, then information must have:

*
Accurately

Information free from mistakes and doesn't deflect or mislead
*
Punctually

Incoming information at receiver may not lose time
*
Relevantly

Information is have benefit for its usage.

Information will be valuable if big added significance of expense get it