review of class 1 · class 2: database system concepts and architecture review of class 1 2...

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ITCS 3160DATA BASE DESIGN AND IMPLEMENTATIONJING YANG2010 FALL

Class 2: Database System Concepts and Architecture

Review of Class 12

DatabaseMDatabase management systems (DBMS)

Concept: Meta-data

Characteristics of database approach Concepts: Program-data and program-operation independence, data abstraction, view

Fundamentals of Database Systems Elmasri and Navathe

Actors on the sceneConcepts: DBA, naïve or parametric user

Workers behind the scene

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Review of Class 1 (cont'd.)3

Advantages of using DBMS approachC D li i d d li i Concept: Data normalization and denormalization, integrity constraints,

A brief history of database applicationsWhen not to use database


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1.9 - What is the difference between controlled and ncontrolled red ndanc ?and uncontrolled redundancy?


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Outline

Data Models, Schemas, and InstancesA

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Three-Schema Architecture and Data IndependenceDatabase Languages and InterfacesThe Database System EnvironmentCentralized and Client/Server Architecturesfor DBMSsClassification of Database Management Systems


Data Abstraction

Data abstraction S i f d il f d i i d

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Suppression of details of data organization and storageHighlighting of the essential features for an improved understanding of data


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What is a Data Model

Data modelC ll i f h d ib h f

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Collection of concepts that describe the structure of a databaseProvides means to achieve data abstractionBasic operations • Specify retrievals and updates on the database

Dynamic aspect or behavior of a database Dynamic aspect or behavior of a database application• Allows the database designer to specify a set of valid

operations allowed on database objects


Categories of Data Models

High-level or conceptual data models Cl h i d

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Close to the way many users perceive data

Low-level or physical data models Describe the details of how data is stored on computer storage media

Representational or implementation data modelsEasily understood by end users Also similar to how data organized in computer storage


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Conceptual Data Models

Entity R l ld bj

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Represents a real-world object or concept

AttributeRepresents some property of interest Further describes an entity

Relationship among two or more entities Represents an association among the entities

Entity-Relationship model


Representational Data Models

Relational data modelU d f l i di i l i l DBMS

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Used most frequently in traditional commercial DBMSs

Legacy network and hierarchical models

Record-based data models refer to relational, network, and hierarchical data modelsObject data model

New family of higher-level implementation data models Closer to conceptual data models


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Physical Data Models

Describe how data is stored as files in the computerRepresent information s ch as record formats

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Represent information such as record formats, record ordering, and access path Access path • Structure that makes the search for particular database

records efficientIndex Index • Example of an access path • Allows direct access to data using an index term or a

keyword


Database Schema

Database schemaD i i f d b

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Description of a database

Schema diagramDisplays selected aspects of schema

Schema constructEach object in the schema


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Schema Diagram of the University Database


Database State

Database state or snapshotData in database at a particular moment in time

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Also called the current set of occurrences or instances in the databaseEach schema construct has its own current set of instances

Define a new databaseSpecify database schema to the DBMS onlyDatabase is in empty state with no data

Initial state Initial state Populated or loaded with the initial data

Valid stateSatisfies the structure and constraints specified in the schema


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Schema evolution

Changes applied to schema as application req irements change

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requirements changeMost modern DBMSs include operations for schema evolution


Three-Schema Architecture

Internal level D ib h i l f h d b

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Describes physical storage structure of the database

Conceptual levelDescribes structure of the whole database for a community of users

External or view level Describes part of the database that a particular user group is interested in


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Three-Schema Architecture (cont'd.)17


Data Independence

Capacity to change the schema at one level of a database system

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yWithout having to change the schema at the next higher levelOnly the mapping between the two levels is changed

Types:Logical Data Independence

Change conceptual schema without changing external schemas or application programsapplication programs

Physical Data IndependenceChange internal schema without having to change conceptual schema


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DBMS Languages

Data definition language (DDL)• Defines both conceptual and internal schemas or conceptual

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p pschema only

Storage definition language (SDL)• Specifies the internal schemaView definition language (VDL)• Specifies user views/mappings to conceptual schemaData manipulation language (DML)p g g ( )• Allows retrieval, insertion, deletion, modification

• Comprehensive integrated language such as SQL• SQL is a combinations of DDL, VDL, and DML


DBMS Languages (cont'd.)

Data manipulation language (DML)Hi h l l d l DML

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High-level or nonprocedural DML • Can be used on its own to specify complex database

operations concisely• Set-at-a-time or set-oriented

Low-level or procedural DML • Must be embedded in a general-purpose programming g p p p g g

language• Record-at-a-time


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DBMS Interfaces

Menu-based interfaces for Web clients or browsingf

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Forms-based interfacesGraphical user interfacesNatural language interfacesSpeech input and outputInterfaces for parametric usersInterfaces for parametric usersInterfaces for the DBA


The Database System Environment

DBMS component modulesBuffer management

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gSchedule disk read/write

Stored data manager Control access to DBMS information stored on disk

DDL compiler Process schema definitions, stored schemas into catalog

Interactive query interface• Query compiler • Query compiler

• Parse and validate queries and compleile them into an internal form • Query optimizer

• Rearrange and reorder operations, eliminate redundancies, chose algorithms and index


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The Database System Environment (cont'd.)

DBMS component modulesPrecompiler

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PrecompilerExtract DML commands from an application program Send them to DML complier

Runtime database processorExecute privileged commends, the executable query plans, and canned transaction with runtime parametersManage buffersWork with System catalog and may update it with statistics

Concurrency control systemBackup and recovery system


24Fundamentals of Database Systems Elmasri and Navathe

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Database System Utilities

LoadingL d i i d fil

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Load existing data filesTransfer data from one DBMS to another

BackupCreates a backup copy of the databaseIncremental backups


Database System Utilities (cont'd.)

Database storage reorganizationR i f d b fil i diff fil

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Reorganize a set of database files into different file organizations

Performance monitoringMonitors database usage and provides statistics to the DBA


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Tools, Application Environments, and Communications Facilities

CASE ToolsU d i h d i h

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Used in the design phase

Data dictionary (data repository) systemStores design decisions, usage standards, application program descriptions, and user information

Application development environments

Communications software


Centralized DBMS Architecture

All DBMS functionality, application program e ec tion and ser interface processing carried o t

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execution, and user interface processing carried out on one machine


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Basic Client/Server Architectures

Servers with specific functionalitiesFile server

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File server • Maintains the files of the client machines.Printer server • Connected to various printers; all print requests by the

clients are forwarded to this machineWeb servers

S d t b t t ( t ) h t i d Send out web content (pages, etc.) when a request is made by a web browser clientA website itself is hosted on the web server

e-mail servers


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Basic Client/Server Architectures (cont'd.)

Client machines P id i h

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Provide user with:• Appropriate interfaces to utilize these servers• Local processing power to run local applications


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Basic Client/Server Architectures (cont'd.)

Client U hi h id i f bili i

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User machine that provides user interface capabilities and local processing

ServerSystem containing both hardware and software Provides services to the client machines• Such as file access, printing, archiving, or database access


Two-Tier Client/Server Architectures for DBMSs

Server handlesQ d i f i li l d SQL

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Query and transaction functionality related to SQL processing

Client handlesUser interface programs and application programs


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Two-Tier Client/Server Architectures (cont'd.)

Open Database Connectivity (ODBC) P id li i i i f (API)

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Provides application programming interface (API)Allows client-side programs to call the DBMS• Both client and server machines must have the necessary

software installed

JDBCAll J li t t Allows Java client programs to access one or more DBMSs through a standard interface


Three-Tier and n-Tier Architectures for Web Applications

A li ti W b

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Application server or Web serverAdds intermediate layer between client and the database serverRuns application programs and stores business rules

N-tierDivide the layers between the user and the stored data further into finer components


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Classification of DatabaseManagement Systems

Data modelR l i l

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• Relational• Object• Hierarchical and network (legacy)• Native XML DBMS

Number of users• Single-user• Multiuser


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Classification of DatabaseManagement Systems (cont'd.)

Number of sites• Centralized

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• Centralized• Distributed

• Homogeneous• Use the same DBMS software at all the sites

• Heterogeneous• Use different DBMS software at each sites

Cost• Open source• Different types of licensing


Classification of DatabaseManagement Systems (cont'd.)

Types of access path options

G l i l

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General or special-purpose


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Network Model41


Summary

Concepts used in database systemsM f

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Main categories of data modelsTypes of languages supported by DMBSsInterfaces provided by the DBMSDBMS classification criteria:

Data model, number of users, number of sties, access Data model, number of users, number of sties, access paths, cost


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After Class Exercise43

2.12 - Think of different users for the database of Figure 1 2 What type of applications would each user Figure 1.2. What type of applications would each user need? To which user category would each belong and what type of interface would they need?

2.14 - if you were designing a Web-based system to make airline reservations and to sell airline tickets


make airline reservations and to sell airline tickets, which DBMS Architecture would you choose from Section 2.5? Why? Why would the other architectures not be a good choice?

review of class 1 · class 2: database system concepts and architecture review of class 1 2...

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