pert4-5 database design

8/9/2019 Pert4-5 Database Design

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Database DesignSession 4 and 5

Matakuliah : Web Database

Tahun : 2008


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Last Session Review:

Web Basic ConceptHow to put information on WebDynamic Web pages

New Development of Web


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Agenda:Conventional Database DesignMethodRequirements AnalysisData AnalysisData Design

Physical Database Design


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Objectives:Student understand ConventionalDatabase Design MethodStudent can do RequirementsAnalysis, Data Analysis, Data Designand Physical Database Design

Student can design conceptualdata model and ERD


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Conventional Database Design Method

What is Database Design?

Process of creating a design for a database that will support theenterprises operations and objectives

Major Aims for Database Design?

Represent data and relationship between data required by allmajor application area and users groups

Provide data model that support any transactions required onthe data

Specify a minimum design that is appropriately structured toachieve stated performance requirements for the system

Two main approaches in Database Design?

Entity Relationship Diagram (ERD), for Relational Database

UML, for Object Data Modeling


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(cont.)


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(cont.) Steps in Database Design Method? Requirements Analysis

Data Analysis

Data Design


Input in Database Design Method? The Organization: serve as sponsor of new system

Output in Database Design Method?

Description of the Organization and System Requirements

Conceptual Data Model

Logical Data Model

Physical Data Model


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Requirements Analysis

What is Requirements Analysis?

The process of collecting and analyzing information about thepart of the organization that is to be supported by thedatabase system, and using this information to identify therequirement for the new system

Technique to do Requirement Analysis?

Observation

Interview

Inspecting Documents

Surveying Experts Using Other Information

Output from Requirements Analysis?

Description of the organization and system requirements


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Requirements Analysis (cont.)

Study Case Requirements Analysis

Assume that you are developing a database

system for your enterprise, whether it is auniversity (or college) or business (ordepartment). Consider what technique you woulduse to identify the important facts needed todevelop a database system.


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Data Analysis

What is Data Analysis? The process of describing the organization in terms of

the phenomena that must be represented within thedatabase.

How to do Data Analysis?

There are 2 approach: Top-Down

Bottom-Up

Output from Data Analysis? Conceptual Data Model


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Data Analysis (cont.) 3 Component in Database:

Entity

should be unique and has name. Represent objects or things inreal world that has independent existence.

Example: Student Entity

Representation:Or

Relationship

connection between one entity with another.

Example: Relationship between student entity and faculty entity Representation:

Or

x


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Data Analysis (cont.)

3 Component in Database: Attribute

Fact-fact that describe entity or relationship

Example: Nim and Name attribute in Entity

Representation:

Or


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2 Approach of Data Analysis that are commonly used?

Top-Down

Top-down=entity-relationship-attribute data analysis

How:

Identify entities: usually represent the real world

Identify relationships between entities: identify direct relationship only

Identify entities attributes: fact about entities that must represent indatabase

Advantages:

Represent real world

Filter out entities, relationships and attributes that do not make sense

or not useful within the context of problem

Appropriate for complex database with many attributes

Disadvantages:

Often result in a simpler conceptual model


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2 Approach of Data Analysis that are commonly used?

Top-Down

Example:

University has students and faculty.

Create Students and Faculty entity.

Students and Faculty has direct relationship, which is: Students chooseFaculty. Choose is relationship.

Students has nim, name, address, place of birth and date of birth, whileFaculty has faculty code, faculty name and dean. Those are the attributes.


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Data Analysis (cont.) 2 Approach of Data Analysis that are commonly used?

Bottom-Up Bottom-Up=attribute-relationship-entity data analysis

Based on the notion that entities are implicit in the data values

How:

Identify data item (attribute): identified from fields on data recordingform or contents of organizations files and records

Identify relationships between data items: identify connectionbetween one data item with the others

Identify entities: deducted from the attributes and relationshipsidentified in step 1 and 2

Advantages: Appropriate for simple database design

Give attention on detail attributes

Disadvantages: Hard to use in complex database design


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Data Analysis (cont.) 2 Approach of Data Analysis that are commonly used?

Bottom-Up

Example:

University has student data form.

In that form, there are several field that can be filled. Those fields are: nim,name, address, place of birth, date of birth, faculty code, faculty name and

dean. Those are the attributes.

Find relationship between those data items. Nim, name, address, place ofbirth and date of birth are describing one entity and faculty code, name anddean are describing one entity.

Separate those attributes and relationships into entities Students and Facultyentities.


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2 Approach of Data Analysis that are commonlyused? Those 2 approach can be combine, depend on the

situations and needs.

Other Approach: Inside-Out: related to the bottom-up approach but differ by

the first identifying a set of major entities and thenspreading out to consider other entities, relationships andattributes associated with those first identified


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Type of Relationships between entities? One-to-one

One-to-many

Many-to-many

Zero-or-one-to-many

Model composite key and generalization/specification


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Data Analysis (cont.) Case Study for Data Analysis

Consider the following statement and use both top-down andbottom-up technique:

Students attending Honley University enroll on courses.There are prerequisites for enrollment, i.e. the student musthave certain qualifications, or be accepted by Dr. Brown theadmissions tutor. The institute currently has 3000 students

enrolled. Once enrolled, the student will accumulate creditsby taking various course modules, such as Programming andObject Database. A grade is awarded for each completedmodules. The grade will be A, B, C, D or E. A representsdistinction, and E a fail. Students may be full time or parttime.


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Data Design

What is a Data Design? The process of defining a logical data model that

implements the conceptual model as a database

Input Data Design? Conceptual data model

How to do Data Design? Transform conceptual data model into a relational

database by applying several rules

Normalization

Output from Data Design? ERD Normal


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Data Design (cont.) Rules to transform?

Representation of Entities

Each entity in the Conceptual data model becomes a table. Eachproperty become attribute. A primary key is selected

One-to-one

Transform into 1 table

One-to-many

Transform into 2 tables

Primary key in one (parent or owner) table migrates to many(child or member) table (become foreign key). Each row in many

table many cross-reference a row in the one table. Many-to-many

Replaced by two one-to-many relationships

Zero-or-one-to-many

Represented by a separate table, in the same way that one-to-many relationships are


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Data Design (cont.)

Normalization? First Normal Form (1NF):

simplifying the structure in a database

Ensure each data value represent a single fact

Select Primary Key Eliminate redundancy and calculation

Second Normal Form (2NF):

Eliminate partial dependency

Third Normal Form (3NF):

Eliminate transitive dependency


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Data Design (cont.)

Case Study 1 for Data Design?

Represent the following structure as ERD model:

The university of Honley is a technical university,with five faculties, each with departments


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Data Design (cont.)

Case Study 2 for Data Design?

A relational table is designed to represent details

of projects. Its columns are project number,employee number of project leader, projectname, host department and head of hostdepartment. Each project has a unique number, aleader and a host department. Each department

has only one head, but can host many projects.

Make the 3NF from this case.


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What is a Physical Database Design? The phase in design process wherein the designer

decides how the database is to be stored in DBMS.Highly connected with DBMS.

Will be discuss in details in Session 8


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Summary

Requirements Analysis: process to collect andanalyze needs from the organization

Data Analysis: derives a conceptual model of thedatabase. Most commonly used technique: top-down and bottom-up.

Data Design: derives a ERD Normal.

Physical Database Design: highly connected withDBMS.


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Next Session:Complication in Web DatabaseLimitation in Web Database Method

Web Database Design MethodWeb Data AnalysisLogical Web Data Design

Physical Web Database DesignReview session 1-7


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End of

Database Design

Thank you