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Concepts of Database Concepts of Database Management, Fifth Management, Fifth
EditionEdition
Chapter 9:Chapter 9:
Database Management Database Management ApproachesApproaches
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Objectives
Describe distributed DBMSs
Discuss client/server systems
Define data warehouses and explain their structure and access
Discuss the general concepts of object-oriented DBMSs
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Objectives
Summarize the impact of Web access to databases
Provide a brief history of database management
Describe the network and hierarchical data models
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Distributed Databases
Computers at various sites
Connected with communications network
Distributed database is single logical database physically divided among networked computers
DDBMS supports and manipulates distributed databases
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Figure 9.1: Communications Network
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Characteristics ofDistributed DBMSs
Homogeneous
Same local DBMS at each site
Heterogeneous
At least two sites with different DBMSs
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Characteristics ofDistributed DBMSs (con’t.)
Location transparency User feels as though entire database is at their
site
Replication transparency User unaware of behind the scenes replication
of the data Fragmentation transparency
Logical object divided among various locations
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Unfragmented Parts Table
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Fragmented Parts Table
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Advantages of Distributed Databases
Local control of data Possible legal reasons for local control over data
used in a particular geographic region Increased database capability Added system availability
Though parts of a database may not be accessible, transactions can still occur, increasing overall availability of the database
Added efficiency Smaller tables are faster to query
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Disadvantages of Distributed Databases
Problems updating replicated data
More complex query processing
More complex treatment of concurrent update
More complex recovery measures
More difficult management of the data dictionary
More complex database design
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Rules for Distributed Databases Local autonomy
No reliance on a central site
Continuous operation
Location transparency
Fragmentation transparency
Replication transparency
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Rules for Distributed Databases (con’t.)
Distributed query processing
Distributed transaction management
Hardware independence
Operating system independence
Network independence
DBMS independence
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Client-Server Systems
Tiered approach to developing systems
Typical systems will implement two tiers Client
Server
Server manages all access to data
Client consults server for most processing
Some systems almost totally abstract the client from any processing by introducing a middle tier to handle all logic or processing
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Figure 9.4: Client/Server Systems
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Figure 9.5: Two-Tier Client/Server Architecture
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Figure 9.6: Three-Tier Client/Server Architecture
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Advantages ofClient/Server Systems
Lower network traffic
Improved processing distribution
Thinner clients
Greater processing transparency
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Advantages ofClient/Server Systems (con’t.)
Increased network, hardware, and software transparency
Improved security
Decreased costs
Increased scalability
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Triggers and Stored Procedures
Triggers Actions that occurs automatically in response
to a particular database operation
Created by programmers
Use special SQL statements
Stored Procedures Collection of SQL statements compiled and
optimized by DBMS
Improves performance
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Data Warehouses
Subject-oriented, integrated, time-variant, nonvolatile collection of data in support of management’s decision-making process
Used for analysis of existing data
Resolves performance issues suffered by operational RDBMSs and OLTPs
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Figure 9.7:Data Warehouse Architecture
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Figure 9.8:Data Warehouse Structure
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On-Line Analytical Processing
Optimized to work with data warehouses
Used to answer questions
Allows users to perceive data as a multidimensional data cube
Slice and dice
Drill down
Roll Up
Data mining
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Figure 9.9: Data Cube Representation
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Figure 9.11: Slicing on Time Dimension
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Figure 9.12: Dicing on Part Dimension
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Rules for OLAP Systems
Multidimensional conceptual view
Transparency
Accessibility
Consistent reporting performance
Client/server architecture
Generic dimensionality
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Rules for OLAP Systems
Dynamic sparse matrix handling
Multiuser support
Unrestricted, cross-dimensional operations
Intuitive data manipulation
Flexible reporting
Unlimited dimensions and aggregation levels
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Object-Oriented DBMS (OODBMS)
System in which data and methods operating on that data are encapsulated into objects
Store graphics, drawings, video, sound, and other complex objects called binary large objects (BLOBs)
General concepts Objects and classes
Methods and messages
Inheritance
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Unified Modeling Language (UML)
Models various aspects of software development for OO systems
Includes several types of diagrams Class Use Case State Sequence Activity Collaboration Component
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Figure 9.19: Class Diagram for Premiere Products
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Figure 9.20: Class Diagram with Constraints
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Figure 9.21:Class Diagram with a Generalization and a Constraint
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Rules for OODBMSs
Complex objects
Object identity
Encapsulation
Information hiding
Types of classes
Inheritance
Late binding
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Rules for OODBMSs (con’t.)
Computational completeness
Extensibility
Persistence
Performance
Concurrent update support
Recovery support
Query facility
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Web Access to Databases
Electronic Commerce
Conducting business on the Internet
Business to Business
Business to Consumer
Internet facilitating better access to data
Extensible Markup Language (XML)
Key technology to data interchange between systems
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Figure 9.22: Web Access to Databases
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History of Database Management
Early systems
GUAM, DL/I, IMS, IDS, IDMS
Relational products
DB2, Oracle, Sybase, Paradox, dBASE, Access, MySQL, SQL Server
OODBMSs
Gemstone, Objectivity/DB, Versant
ORDBMSs
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Hierarchical and Network Databases
Data models have two components, structure and operations Structure is how users perceive data to be
structured Operations are facilities given to users to interact
with data Users perceive a network model database as a
collection of record types and relationships Users perceive a hierarchical model as a
collection of hierarchies or trees
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Summary Distributed databases physically fragment a
database across many parts of a DBMS, but they must maintain reasonable transparency
Most applications built around a DBMS will use a client-server architecture, involving at least two tiers, but more typically three
Data warehouses are specialized DBMS products that allow users to view the data in more than two dimensions, typically three
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Summary (con’t.)
Object Oriented databases provide an encapsulated view by merging data with their operations, fitting with modern programming architectures
Web access is common way to access data in a DBMS
Hierarchical and network data models are two models of how users perceive a DBMSs structure and operation