Database Environment

1
Chapter 2

• Database Environment

2
Agenda

• Three-Level ANSI-SPARC Architecture
• Database Languages
• Data Models
• Functions of DBMS
• Components of DBMS
• Data Dictionary Information Resource Dictionary
  System

3
Three-Level ANSI-SPARC Architecture

• External
• User's view
• Conceptual
• Organization view
• Constraints, security, integrity
• Internal
• Physical presentation
• Storage, security, encryption

4
Database Schemas

• Database schema (intension) database instance
  (extension)
• External schemas (subschema)
• Conceptual schema
• Internal schema

5
Mapping

• External/conceptual mapping
• Conceptual/internal mapping
• Example

6
Data Independence

• Logical data independence
• Physical data independence

7
Database Languages

• Data Definition Language (DDL)
• Structured Query Language (SQL)
• Data Manipulation Language (DML)
• Procedural DML
• Non-procedural DML
• Structured Query Language (SQL)
• Query-by-Example (QBE)
• Fourth-Generation Language
• Form, report, graphics, application generators

8
Data Models

• Definition
• Integrated concept for describing data,
  relationship and constraints
• Types
• Object-based data models
• Record-based data models
• Physical data models (internal structure,
  ordering, paths)

9
Object-Based Data Models

• Entity-relationship
• Entity, attribute, relationship
• Usage
• Object-oriented
• Object, class, subclass, inheritance, state
  (attributes), behavior (methods or actions),
  encapsulation, message, polymorphism
• Usage

10
Record-Based Data Models

• Relational data model
• Network model
• Hierarchical Model

11
Relational Data Model

• Terminology
• Relations
• Attributes
• Tuples
• Record relationship
• One-to-many relationship
• Usage
• Ad hoc reporting
• Example

12
Network Model

• CODASYL DBTG
• Integrated Date Store (IDS)
• Terminology
• Data item group item
• Record type (owner, member)
• Set type optional, mandatory, permanent
• Schema sub-schema

13
Network Model

• Set
• Owner member
• Singular or system
• Pointer chains (single-linked, doubly linked,
  member-to-owner)
• Record relationship
• Many-to-many relationship
• Usage
• Large volume transaction processing

14
Network Model

• Schema DDL
• Schema description
• Area description
• Record Description
• Set description
• Data Manipulation Language (DML)
• Host language
• Sub-schema DDL

15
Hierarchical Model

• IBM
• Information Management Systems
• Terminology
• Tree, general tree, subtree
• Nodes, root node, child nodes
• Segment type
• Record relationship
• One-to-many relationship
• Excellent referential integrity
• Inflexible
• No many-to-many relationship

16
Hierarchical Model

• Hierarchical record structure (pointer or
  address)
• Level of tree (significant - insignificant)
• Pre-order traversal or top down
• Post-order traversal or bottom up
• Twin pointers, forward links, backward links,
  logical pointers
• Usage
• Large volume transaction processing

17
Functions of a DBMS

• Data storage, retrieval and update
• A user-accessible catalog
• Transaction support
• Concurrency control
• Recovery
• Authorization
• Integrity
• Data independence
• Data communication
• Other Utilities

18
Components of a DBMS

• Query processor
• Database manager
• File manager
• DML preprocessor
• DDL compiler
• Catalog manager

19
Components of Database Manager

• Authorization control
• Command processor
• Integrity checker
• Query optimizer
• Transaction manager
• Scheduler
• Recovery manager
• Buffer manager

20
SYSTEM CATALOGS

• Definition
• Data dictionary
• Information about database
• Types
• Active
• Passive
• Integrated
• Standalone

21
Information Resource Dictionary System (IRDS)

• IRDS standards by ISO
• A set of rules to store and access information in
  the data dictionary
• Objectives data extensibility, data integrity,
  data access control
• Service interface works with panel, command
  language, export/import files, application
  programs

22
Points to Remember

• Three-Level ANSI-SPARC Architecture
• Database Languages
• Data Models
• Functions of DBMS
• Components of DBMS
• Data Dictionary Information Resource Dictionary
  System

23
Assignment

• Review chapter 1-2, appendix c
• Read chapter 3 4 (skip relational calculus 4.2)