Data Management Systems Design

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Data Management Systems Design

• CIS 631 Lecture Notes 2
• Cyril S. Ku

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Data Model
Data Model - a set of concept to describe the
data types, relationships,
constraints, operations, etc. of
a database.
(Conceptual) High Level
e.g. Entity
Object-Oriented Relationship
Model Relational,
Object-Oriented Network,
Database Hierarchical
(Logical)
(Physical) Low Level
Computer Storage
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User 1
User 2
User n
External (Individual Users)
View A
View Z
DBMS
Conceptual View
Conceptual (DBA)
Physical View
Internal (Physical)
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Database Schema - description of a database
(meta-data) e.g. Student (Name, SSN, Class,
Major)
Student
abc 1234 senior cs
Intensional DB (variable or data item in
programming language)
Instances - data in a database (values in
programming language) -
extensional DB Database State - one set of
instances to another -
transition of valid DB state to valid DB state
is part of the job of
DBMS.
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Logical Data Independence
Database Schemas
Schema Changes
Not affecting application programs
uses
Application Program
Physical Data Independence - changes to
physical storage, not affecting database
schema. Data Definition Language (DDL) - defines
database schemas. Data Manipulation Language
(DML) - retrieval, insertion, deletion,
modification of data - SQL is both DDL and
DML DML embedded in a programming language
Host Language
Data Sub-language