Database Technology

1
Database Technology

• Soochow University Library
• Chen Jiacui

2
Outline

• Introduction
• File Management Problems
• Databases
• Types of database
• Hierarchical
• Network
• Relational
• Nested
• Proprietary
• Text Retrieval Systems or "Free Form" Databases
• Object Oriented DBMS (OODBMS)
• Hybrids
• The Future

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Introduction to the library systems

• The Formative Years of Library Systems (by the
  mid-sixties)
• Early library systems developed their own systems
  for storing and retrieving records
• Commercial products involved
• commercial products began to appear that offered
  advantages to application developers

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File Management Data Hierarchy
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Accessing Records from Computer Files

• In sequential file organization, data records
  must be retrieved in the same physical sequence
  in which they are stored
• In direct or random file organization, users can
  access records in any sequence, without regard to
  actual physical order on the storage medium
  this is especially important to efficiently
  access information online

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Problems Arising from theFile Environment

• Organizations typically began automating one
  application at a time
• These systems grew independently without overall
  planning
• The registrar, accounting, and athletic
  departments in a university often had independent
  information systems which included common
  functions which were each separately designed,
  coded, tested, and documented at great expense

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Other File Management Problems

• Data redundancy
• the same data could be duplicated in several
  files
• Data inconsistency
• actual values across various copies of the data
  no longer agree
• Data isolation
• data in different systems may be stored
  differently making it more difficult to access
• Security
• new applications may be added on an ad-hoc basis
• Data integrity
• the values in data fields often must be in valid
  ranges, but this is difficult to maintain across
  multiple data files
• Application/data independence
• applications are dependent on data format

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Databases

• Database technology attempts to minimize the
  problems associated with traditional file
  management
• A database is an organized logical grouping of
  related files
• In a database, data are integrated and related so
  that one set of software provides access to all
  the data, alleviating problems associated with
  data redundancy, data isolation, and data
  inconsistency

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Database Management Systems (DBMSs)

• A program (or group of programs) that provides
  access to a database is known as a database
  management system (DBMS)
• The DBMS permits an organization to centralize
  data, manage them efficiently, and provide access
  to stored data by application programs
• The DBMS acts as an interface between application
  programs and physical data files and provides
  users with tools to add, delete, display, print,
  search, select, sort, and update data

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Data Life Cycle Process
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Advantages and Capabilities of a DBMS

• Access and availability of information can be
  increased
• Data access, utilization, security, and
  manipulation can be simplified
• Data inconsistency and redundancy is reduced
• Program development and maintenance costs can be
  dramatically reduced
• Captures/extracts data for inclusion in databases
• Interrelates data from different sources
• Quickly retrieves data from a database for
  queries and reports

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Advantages and Capabilities of a DBMS (cont.)

• Provides comprehensive data security
• Handles personal and unofficial data so that
  users can experiment with alternative solutions
  based on their own judgment
• Performs complex retrieval and data manipulation
  tasks based on queries
• Tracks usage of data
• Flexibility of information systems can be
  improved
• Application-data dependence can be reduced by
  separating the logical view of data from its
  physical structure and location

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DBMS Languages

• A DBMS contains four major components
• data model
• Defines the way data are conceptually structured
• data definition language (DDL)
• specifies the content and structure of the
  database (schema)
• data manipulation language (DML)
• enables manipulation of the data in the database
• data dictionary
• stores definitions of data elements and data
  characteristics such as usage, physical
  representation, ownership, authorization, and
  security
• Structured query language (SQL) is the most
  common language for performing data definition
  and data manipulation

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DBMS Benefits

• Improved strategic use of corporate data
• Reduced complexity of the organizations
  information systems environment
• Reduced data redundancy and inconsistency
• Enhanced data integrity
• Application-data independence
• Improved security
• Reduced application development and maintenance
  costs
• Improved flexibility of information systems
• Increased access and availability of data and
  information

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Logical Data Organization

• A managers ability to use a database is highly
  dependent on how the database is logically
  structured
• There are three basic models for logically
  structuring databases hierarchical, network, and
  relational
• The relational model is the one that is most
  commonly used

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The Relational Database Model

• Most data have traditionally been organized into
  tables of columns and rows
• The relational model is based on this simple
  concept of tables
• In a relational database, the tables are called
  relations, each row of data (tuple) is equivalent
  to a record, and each column of data (attribute)
  is equivalent to a field
• A database is typically designed as a collection
  of one or more related tables
• The advantage is that it is a conceptually simple
  and highly flexible method for storing data
• The disadvantage is that processing efficiency
  and speed are lower when compared with
  hierarchical and network databases

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Types of database

• Hierarchical
• Network
• Relational
• Nested
• Proprietary
• Text Retrieval Systems or "Free Form" Databases
• Object Oriented DBMS (OODBMS)

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History of Database Systems

• First-generation
• Hierarchical and Network
• Second generation
• Relational
• Third generation
• Object Relational
• Object-Oriented

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Hierarchical Database Model

• History
• North American Rockwell developed GUAM
  (Generalized Update Access Method)
• Mid 1960s Rockwell partner with IBM to create
  Information Management System (IMS)
• IMS DB/DC lead the mainframe database market in
  70s and early 80s
• Represents well hoe components are decomposed
  into parts

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Hierarchical Database Model (cont.)

• Logically represented by an upside down tree
• Each parent can have many children
• Each child has only one parent

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Hierarchical Database Model (cont.)

• Advantages
• Conceptual simplicity
• Database security and integrity
• Data independence
• Efficiency
• Disadvantages
• Complex implementation
• Difficult to manage and lack of standards
• Lacks structural independence
• Applications programming and use complexity
• Implementation limitations (no MN relationship)

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Network Database Model

• History
• CODASYL (Conference on Data Systems Languages)
  created a group to work on standardization of
  databases Database Task Group (DBTG)
• Identified 3 database component
• Network schema (database organization)
• Subschema (views of database per user)
• Data management language

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Network Database Model (cont.)

• Each record can have multiple parents
• Composed of sets - relationships
• Each set has owner record and member record
• Member may have several owners
• A set represents a 1M relationship between the
  owner and the member

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Network Database Model (cont.)

• Advantages
• Conceptual simplicity
• Handles more relationship types
• Data access flexibility
• Promotes database integrity
• Data independence
• Conformance to standards
• Disadvantages
• System complexity
• Lack of structural independence

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Relational Database Model

• First developed by E.F. Codd (IBM) in 1970
• First deployed on mainframe computers (DB2), then
  also personal computers
• Oracle, Informix, SQL server, DB2

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Relational Database Model (cont.)

• Perceived by user as a collection of tables for
  data storage
• Tables are a series of row/column intersections
  (a row corresponds to a record, a column to a
  field)
• Tables related by sharing common entity
  characteristic(s)
• RDBMS

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Relational Database Model (cont.)
Figure 1.11
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Relational Database Model (cont.)

• Advantages
• Structural independence
• Improved conceptual simplicity
• Easier database design, implementation,
  management, and use
• Ad hoc query capability with SQL
• Powerful database management system

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Relational Database Model (cont.)

• Disadvantages
• Substantial hardware and system software overhead
• Poor design and implementation is made easy
• May promote islands of information problems

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Nested databases

• Advantages
• Fast and flexible development
• Low administrative costs
• More efficient
• Disadvantages
• Minor market segment
• Data corruption
• query language was "not SQL"

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Proprietary databases

• Almost every library system supplier and library
  itself are continuing to maintain and develop
  their own DBMS

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Proprietary databases

• Advantages
• Database designed around the problems and
  idiosyncrasies
• Speed of response to problems
• Disadvantages
• Lack of compliance with standards
• System migration

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Text Retrieval Systems

• Advantages
• Powerful search and retrieve functions
• Hybrid systems
• Disadvantages
• Lack of authority files
• Ignore some retrieval functions

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Object Oriented DBMS
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References

• http//www.biblio-tech.com/html/databases.html
• http//www.cbpa.drake.edu/strader/is101.htm
• http//courses.washington.edu/tcss445/tcss445A_1.p
  pt407,25,Hierarchical Database Model