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Entity Relationship Model

=> Entity,

  • Definition, entity is an object that exists and is distinguishable from other objects.
  • Example :  specific person, company, event, plant.
  • An entity set ?, Entity set is a set of entities of the same type that share the same properties.Example: set of all persons, companies, trees, holidays

=> Attributes,

  • Definition, attributes is  An entity is represented by a set of attributes, that is descriptive properties possessed by all members of an entity set.
  • Example:

customer = (customer-id, customer-name,        customer-street, customer-city)
loan = (loan-number, amount)

  • domain – the set of permitted values for each attribute
  • Attribute types:
  1. Simple and composite attributes.
  2. Single-valued and multi-valued attributes.E.g. multivalued attribute: phone-numbers.
  3. Derived attributes.Can be computed from other attributes.E.g.  age, given date of birth

=> Relationship,

  • Definition, a relationship is an association among several entities.
  • Example:
HayesdepositorA-102
customer entity  relationship set  account entity
  • A relationship set is a mathematical relation among n >= 2 entities, each taken from entity sets {(e1, e2, … en) | e1  Î E1, e2 Π E2, …, en Π En} where (e1, e2, …, en) is a relationship.
  • Example:

(Hayes, A-102) Î depositor

 

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Introduction Database #4

=> Database User

  • Users are differentiated by the way they expect to interact with the system.
  • Application programmers – interact with system through DML calls.
  • Sophisticated users – form requests in a database query language.
  • Specialized users – write specialized database applications that do not fit into the traditional data processing framework.
  • Naïve users – invoke one of the permanent application programs that have been written previously.

=> Database Administrator

  • Coordinates all the activities of the database system; the database administrator has a good understanding of the enterprise’s information resources and needs.
  • Database administrator’s duties include:
  1. Schema definition.
  2. Storage structure and access method definition.
  3. Schema and physical organization modification.
  4. Granting user authority to access the database.
  5. Specifying integrity constraints.
  6. Acting as liaison with users.
  7. Monitoring performance and responding to changes in requirements.

=> Transaction Management

  • A transaction is a collection of operations that performs a single logical function in a database application.
  • Transaction-management component ensures that the database remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.
  • Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.

=> User Management

  • Storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.
  • The storage manager is responsible to the following tasks:
  1. Hinteraction with the file manager
  2. efficient storing, retrieving and updating of data

Introduction Database #3

=> Data Definition Language, specification notation for defining the database schema.

 

=> Data Manipulation Language, language for accessing and manipulating the data organized by the appropriate data model.
=> SQL, widely used non-procedural language
  • E.g. find the name of the customer with customer-id 192-83-7465
select   customer.customer-name
from     customer
where  customer.customer-id = ‘192-83-7465’
  • E.g. find the balances of all accounts held by the customer with customer-id 192-83-7465
select   account.balance
from     depositor, account
where  depositor.customer-id = ‘192-83-7465’ and
depositor.account-number = account.account-number

Introduction Database #2

=> Instance and scheme?, Similar to types and variables in programming languages

  • Scheme, the logical structure of the database
  1. e.g., the database consists of information about a set of customers and accounts and the relationship between them)
  2. Analogous to type information of a variable in a program
  3. Physical schema: database design at the physical level
  4. Logical schema: database design at the logical level
  • Instance, the actual content of the database at a particular point in time.
  1. HAnalogous to the value of a variable

=> Data model, a collection of tools for describing; data, data relationships, data semantics, data constraints. Example; Entity Relational Model, Relational Model, object-oriented model, semi-structured data models, Older models: network model and hierarchical model

  • Entity Relationship, E-R model of real world;
  1. Entities (objects),E.g. customers, accounts, bank branch
  2. Relationships between entities,E.g. Account A-101 is held by customer Johnson, Relationship set depositor associates customers with accounts
Widely used for database design, Database design in E-R model usually converted to design in the relational model (coming up next) which is used for storage and processing.

Introduction Database #1

Tomorrow for basdat’s exam,prepared for the subject where lecture had given, and this is a summary from “database system concept -silberscchatz, korthand, sudarshan-“, hope any all of you where read this blog can comment fo the correction maybe, enjoy =)

=> What is database system?, Collection of interrelated data, DBS contains information about a particular enterprise, DBMS:  DBS together program to access the DBS.

=> Example database applications:

  • Banking: all transactions
  • Airlines: reservations, schedules
  • Universities:  registration, grades
  • Sales: customers, products, purchases
  • Manufacturing: production, inventory, orders, supply chain
  • Human resources:  employee records, salaries, tax deductions

=> Purpose database system,

  • In the early days, database applications were built on top of file systems
  • Drawbacks of using file systems to store data:Data redundancy and inconsistency; Difficulty in accessing data, Data isolation — multiple files and formats, Integrity problems.
  • Drawbacks of using file systems : Atomicity of updates, Concurrent access by multiple users, Database systems offer solutions to all the above problems.
  • Physical level describes how a record (e.g., customer) is stored.
  • Logical level: describes data stored in database, and the relationships among the data.
  • View level: application programs hide details of data types.  Views can also hide information (e.g., salary) for security purposes.

=> Pengertian, Metode Gauss Seidel digunakan untuk menyelesaikan persamaan serentak. Metode ini lebih cepatdibandingkan dengan Metode Jacobi. Metode Gauss Seidel ini menggunakan persamaan sbb

  • :xin1=biaii−Σj=1i−1 aijaiixjn1− Σj=i1N aijaiix jn
  • persamaan 4.a
  • dimana :i = 1, 2,…Nn = 1, 2, …

=> Algoritma, Algoritma Gauss Seidel, sbb :

  1. Cek apakah susunan persamaan yang akan diselesaikan memenuhi syarat persamaan 4a. Jika ya,maka lanjut ke langkah kedua.
  2. Menyusun matriks koefisien, matriks variabel, dan matriks hasil.
  3. Menentukan titik variabel x awal kemudian melakukan iterasi dengan persamaan 4a hinggadidapatkan nilai variabel x yang tidak berubah atau hampir tidak berubah dari iterasi yangsebelumnya.

=> Download, karena saya gag nyatet adanya y kayak gini, http://www.mediafire.com/?su0874pizkuc98w

metode jacobi di scilab

=> Pengertian, Metode iterasi Jakobi adalah metode penyelesaian persamaan serentak melalui proses iterasi denganmenggunakan persamaan sbb

  • :x1 n1=hi/aii−Σj =1naij/aiix jn…3a
  • dimana j <> i

=>Kelemahan, dari metode ini adalah :

  1. Jika ordo persamaan cukup tinggi maka konsumsi waktu untuk eksekusi program menjadi lama.
  2. Metode ini hanya bisa dipakai jika persamaan yang akan diselesaikan memenuhi syaratpersamaan berikut∣aii∣Σj=1n∣aij∣,i=1,2,… ,Npersamaan3b dimana j <> IBerikut

=>Algoritma, Berikut algoritma Metode Jacobi

  1. Cek apakah susunan persamaan yang akan diselesaikan memenuhi syarat persamaan 3b. Jika ya,maka lanjut ke langkah kedua.
  2. Menyusun matriks koefisien, matriks variabel, dan matriks hasil.
  3. Langkah ketiga adalah menentukan titik variabel x awal kemudian melakukan iterasi denganpersamaan 3a hingga didapatkan nilai variabel x yang tidak berubah atau hampir tidak berubahdari iterasi yang sebelumnya.

=> Download, lihat penerapannya di scilab dengan mengklik link berikut, http://www.mediafire.com/?wbkyebfy9xxphwh