ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT File Organization Terms and Concepts Bit: Smallest unit of data; binary digit (0,1) Byte: Group of bits that represents a single character Field: Group of words or a complete number

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT File Organization Terms and Concepts Record: Group of related fields File: Group of records of same type Database: Group of related files

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT Data Hierarchy in a Computer System Figure 7-1

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT File Organization Terms and Concepts Entity: Person, place, thing, event about which information is maintained Attribute: Description of a particular entity Key field: Identifier field used to retrieve, update, sort a record

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT Entitities and Attributes Figure 7-2

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT Traditional File Processing Figure 7-3

Program-Data dependence Lack of flexibility Poor security ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT Problems with the Traditional File Environment Data redundancy Program-Data dependence Lack of flexibility Poor security Lack of data-sharing and availability

DATA REDUNDANCY The presence of duplicate data in multiple data files Different functions collect the same information independently May have different meanings in different parts of the organisation

Data Redundancy 7

Data Redundancy Staff_Branch relation has redundant data; the details of a branch are repeated for every member of staff. In contrast, the branch information appears only once for each branch in the Branch relation and only the branch number (Branch_No) is repeated in the Staff relation, to represent where each member of staff is located. 8

Program Data Dependence The tight relationship between data stored in files and the specific programs required to update and maintain those files Every program must describe the nature In traditional file environment any changes to data requires a change in all programs that access the data A change in tax rates for example !!

Lack of Flexibility Traditional File system can deliver routine scheduled reports after a significant programming efforts An ad hoc/ unanticipated request for information, would require a lot of time The information is somewhere in the system but too expensive to locate/retrieve Compiling the data could take weeks

Poor Security There is little or no control and management of data Data could be disseminated all over the organisation without control Who is accessing the data and making changes?

Lack of Data-sharing Lack of control over access Hard to get hands on information Different pieces of information in different files and different physical locations Since files in different locations can’t be related hard to share or access in a timely manner Impossible for information to flow freely

Database Technology DATABASE: A collection of data organised to serve many applications efficiently by centralising the data and minimising redundant data.

Historical context Why develop DBMS at all? Manage flood of data from Transaction Processing Systems Integrate data across organisation “Data glare”

DBMS Create, delete, reorganize, and manipulate data in a database A Database Management System (DBMS) is general purpose software and hardware facility to: Create, delete, reorganize, and manipulate data in a database Store, retrieve, share, and maintain data in a database Maintain relationships between the database components

Creates and maintains databases THE DATABASE APPROACH TO DATA MANAGEMENT Database Management System (DBMS) Creates and maintains databases Eliminates requirement for data definition statements Acts as interface between application programs and physical data files

DBMS Cont’d Provide security and procedures relating to privilege and access. Authenticates the integrity of all the updates and transactions that are carried out. interface for the access, deletion and addition of data and for redefining the relationships within the database. A DBMS is a collection of programs that manages the database structure and controls access to the data stored in the database.

DBMS Relieves the programmer or end user from the task of understanding where and how data are actually stored Seperates the logical view from the physical view Logical View- How data perceived by end users or business specialists Physical View- How data is actually organised and structured on phsical storage media

THE DATABASE APPROACH TO DATA MANAGEMENT The Contemporary Database Environment Figure 7-4

Hierarchical and Network DBMS Object-Oriented Databases THE DATABASE APPROACH TO DATA MANAGEMENT Types of Databases Relational DBMS Hierarchical and Network DBMS Object-Oriented Databases

Represents all data in DB as two-dimensional tables called relations THE DATABASE APPROACH TO DATA MANAGEMENT Relational DBMS The most popular type of DBMS today for PCs as well as for larger companies and mainframes Represents all data in DB as two-dimensional tables called relations Similar to flat files but information in more than one file can easily be extracted and combined Relates data across tables based on common data element Examples: DB2, Oracle, MS SQL Server

Relational Data Model Figure 7-6 THE DATABASE APPROACH TO DATA MANAGEMENT Relational Data Model Figure 7-6

Select: Creates subset of rows that meet specific criteria THE DATABASE APPROACH TO DATA MANAGEMENT Three Basic Operations in a Relational Database Select: Creates subset of rows that meet specific criteria Join: Combines relational tables to provide users with information Project: Enables users to create new tables containing only relevant information

Three Basic Operations in a Relational Database THE DATABASE APPROACH TO DATA MANAGEMENT Three Basic Operations in a Relational Database Figure 7-7

Hierarchical DBMS Organizes data in a tree-like structure THE DATABASE APPROACH TO DATA MANAGEMENT Hierarchical and Network DBMS Hierarchical DBMS Organizes data in a tree-like structure Supports one-to-many parent-child relationships Prevalent in large legacy systems

THE DATABASE APPROACH TO DATA MANAGEMENT Hierarchical DBMS Figure 7-8

Hierarchical Disadvantages Knowledge of physical level required Does not support logical data independence and does not support all physical data independence operations Not all problems are one-to-many types Problems with multiple parent implementation Problems with anomalies for parent deletion Application development in 3GL time-consuming Support programs are not part of the DBMS “System created by programmers for programmers!”

Network DBMS Depicts data logically as many-to-many relationships THE DATABASE APPROACH TO DATA MANAGEMENT Network DBMS Depicts data logically as many-to-many relationships

THE DATABASE APPROACH TO DATA MANAGEMENT Network DBMS

Disadvantages Outdated Less flexible compared to RDBMS THE DATABASE APPROACH TO DATA MANAGEMENT Disadvantages Outdated Less flexible compared to RDBMS Lack support for ad-hoc and English language-like queries

Object-Oriented databases Object-oriented DBMS: Stores data and procedures as objects that can be retrieved and shared automatically Object-relational DBMS: Provides capabilities of both object-oriented and relational DBMS

DBMS Disadvantages DBMSs are complex; Need for explicit backup and control; Costs associated with development and operation can be substantial; Consolidation of an entire business’ information resources can create a high level of vulnerability.

Designing Databases Conceptual design: Abstract model of database from a business perspective Physical design: How data is actually stored on direct access storage devices

CREATING A DATABASE ENVIRONMENT Designing Databases Entity-relationship diagram: Methodology for documenting databases illustrating relationships between database entities Normalization: Process of creating small stable data structures from complex groups of data

An Entity-Relationship Diagram Figure 7-10

An Unnormalized Relation of ORDER Figure 7-11

An Normalized Relation of ORDER Figure 7-12

Distributing Databases Centralized database Used by single central processor or multiple processors in client/server network

Distributing Databases Distributed database Stored in more than one physical location Partitioned database Duplicated database

Distributed Databases Figure 7-13

Data warehouse Supports reporting and query tools DATABASE TRENDS Data Warehousing and Datamining Data warehouse Supports reporting and query tools Stores current and historical data Consolidates data for management analysis and decision making

Components of a Data Warehouse DATABASE TRENDS Components of a Data Warehouse Figure 7-16

Datamining Tools for analyzing large pools of data DATABASE TRENDS Data Warehousing and Datamining Datamining Tools for analyzing large pools of data Find hidden patterns and infer rules to predict trends

Improved and easy accessibility to information DATABASE TRENDS Benefits of Data Warehouses Improved and easy accessibility to information Ability to model and remodel the data

Database server Application server DATABASE TRENDS Databases and the Web Database server Computer in a client/server environment runs a DBMS to process SQL statements and perform database management tasks Application server Software handling all application operations

Linking Internal Databases to the Web DATABASE TRENDS Linking Internal Databases to the Web Figure 7-18