Databases : Database Building Procedures 2007, Fall Pusan National University Ki-Joune Li

STEMPNU 2 Importance of Database Application of Databases Garbage-In Garbage-Out About 70% of Development Cost for Information System: DB Cost

STEMPNU 3 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

STEMPNU 4 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 isAs it must be

STEMPNU 5 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

STEMPNU 6 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

STEMPNU 7 Class Diagram: Basic DVD MovieVHS MovieVideo Game Rental Item {abstract} Rental Invoice 1..* 1 Customer Checkout Screen 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.

STEMPNU 8 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

STEMPNU 9 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

STEMPNU 10 Relationship  Relationship between entities  Relationship may have its attributes Example: Male  marriage  Female marriage:

STEMPNU 11 Constraints Conditions  Entity must respect  Relationship must respect Example  Doctor  Operation  Patient Doctor.Major = “Surgeon”

STEMPNU 12 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

STEMPNU 13 Materialization In SQL, view is a virtual table derived from a Select statement  Eample CREATE VIEW ExcellentStudents AS SELECT Name, Department, Score FROM Students WHERE Score > 4.0 SELCT Name FROM ExcellentStudents Where Department=‘CS’ Invoke ExcellentStudents Materialization

STEMPNU 14 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