Database Technology

Database Technology Soochow University Library Chen Jiacui Jane Chen-SUL

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

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

File Management: Data Hierarchy

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

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

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

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

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

Data Life Cycle Process

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

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

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

DBMS Benefits • Improved strategic use of corporate data • Reduced complexity of the organization’s 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

Logical Data Organization • A manager’s 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

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

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

History of Database Systems • First-generation • Hierarchical and Network • Second generation • Relational • Third generation • Object Relational • Object-Oriented

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 70’s and early 80’s • Represents well hoe components are decomposed into parts

Hierarchical Database Model (cont.) • Logically represented by an upside down tree • Each parent can have many children • Each child has only one parent

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 M:N relationship)

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

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 1:M relationship between the owner and the member

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

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

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

Relational Database Model (cont.) Figure 1.11

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

Relational Database Model (cont.) • Disadvantages • Substantial hardware and system software overhead • Poor design and implementation is made easy • May promote “islands of information” problems

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

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

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

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

Object Oriented DBMS

References • http://www.biblio-tech.com/html/databases.html • http://www.cbpa.drake.edu/strader/is101.htm • http://courses.washington.edu/tcss445/tcss445A_1.ppt#407,25,Hierarchical Database Model

Database Technology