Databases : Database Building Procedures

2007, Fall

Pusan National University

Ki-Joune Li

2

STEMPNU

Importance of Database

Application of Databases

Garbage-In Garbage-OutGarbage-In Garbage-Out

About 70% of Development Cost for Information System: DB CostAbout 70% of Development Cost for Information System: DB Cost

3

STEMPNU

Comparison with Software Lifecycle

Requirement Analysis

Functional Specification

Design

Development Environments

Coding

Test

Maintenance

Software Life Cycle – Waterfall Model

Requirement Analysis

Modeling

Schema Design

DB Environments

Data Collection and Input

Quality Control

Maintenance

DB Life Cycle

4

STEMPNU

Requirement Analysis

Analysis of Status as it is and as it shall be.

Output of Analysis Use-Case Diagram of UML: Workflow Analysis Data items that have been maintained and to be maintained Description of each item: Data Dictionary Relationships and Constraints on items Required Correctness

Example: Spatial Correctness, Temporal Correctness

Current State: As it is As it must be

5

STEMPNU

Data Dictionary

Definitions and Representation of Data Items such as Precise definition of data elements Integrity constraints or Constrains Stored procedures and trigger rules Specification of

Producer and Consumer of data element

Why it is so important? Common understanding on data items Consistency of databases Important input to data modeling

6

STEMPNU

Data Modeling

Data Modeling Understanding the real world and application A very small piece of the real world

According to viewpoint Determined by applications

Drawing what you have understood in formal method Class Diagram in UML

4 steps Definition of Entities Attributes of each Entity Relationships Constraints

7

STEMPNU

Class Diagram: Basic

DVD Movie VHS Movie Video Game

Rental Item{abstract}

Rental Invoice

1..*1

Customer

Checkout Screen

0..1

1

Simple

Association

Class

Abstract

Class

Simple

Aggregation

Generalization

Composition

(Dependency)

Multiplicity

MyClassName

+SomePublicAttribute : SomeType

-SomePrivateAttribute : SomeType

#SomeProtectedAttribute : SomeType

+ClassMethodOne()

+ClassMethodTwo()

Responsibilities

-- can optionally be described here.

8

STEMPNU

Extract nouns from Problem statement Use-Case Diagram

Delete unnecessary entities Duplication Attributes rather than entity

ex. Loan amount

Definition of Features Geographic Entity Granularity

Definition of Entities

MyClassName

9

STEMPNU

Definition of Attributes

Attributes of Entity Description of Entity

Photo Images, Names, and etc.. Values

Accuracy Level Different Levels of Detail (LOD)

MyClassName

+SomePublicAttribute : SomeType

-SomePrivateAttribute : SomeType

#SomeProtectedAttribute : SomeType

10

STEMPNU

Relationship

Relationship Relationship between entities Relationship may have its attributes

Example: Male marriage Femalemarriage:

11

STEMPNU

Constraints

Conditions Entity must respect Relationship must respect

Example Doctor Operation Patient

Doctor.Major = “Surgeon”

12

STEMPNU

Schema Design

Automatic Conversion from Data Modeling to Schema

Check Points: Performance Issues Materialization Index

Based on Workload Analysis Distribution of operations Distribution of values

13

STEMPNU

Materialization

In SQL, view is a virtual table derived from a Select statement Eample

CREATE VIEW ExcellentStudents ASSELECT Name, Department, ScoreFROM StudentsWHERE Score > 4.0

SELCT NameFROM ExcellentStudentsWhere Department=‘CS’

Invoke

ExcellentStudents

Materialization

14

STEMPNU

Materialize or Not ?

Materialization Duplication

Not 3NF (BCNF): to be discussed at the end of this course Cause an inconsistency between the original and derived tables Update: Overhead due to update propagation

Extra Space Requirements

Should be determined depending on the WORKLOAD Frequency of updates Cost for update propagation

Especially when materialized view is geographically distributed