THE DATABASE ENVIRONMENT Definitions: Data, Information, Database, MetadataData, Information File Processing Systems The Database Approach Components of the Database Environment Evolution of Database Systems

Data versus Information WestCharles Mann 79154TM Shoes Monthly Sales Report for West Region Sales Rep: Charles Mann Emp No Item Qty Sold Price TM Shoes 1200 $100

Some Definitions Data: Meaningful facts, text, graphics, images, sound, video segments. Database: An organized collection of logically related data. Information: Data processed to be useful in decision making. Information Metadata: Data that describes data. Metadata

Metadata for Class Roster Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and documentation

Three file processing systems at Pine Valley Furniture

Disadvantages of File Processing Systems Program-Data Dependence – data descriptions are included with the application programs that use the data Data Redundancy (Duplication of data) Data Redundancy Limited Data Sharing Lengthy Development Times Excessive Program Maintenance

SOLUTION: The DATABASE Approach Central repository of shared data Data is managed by a controlling agent Stored in a standardized, convenient form Requires a Database Management System (DBMS)

Database Management System DBMS manages data resources like an operating system manages hardware resources DBMS Database containing centralized shared data Application #1 Application #2 Application #3

The Database Approach emphasizes the integration and sharing of data thru the organization An enterprise data model is a graphical model that shows the high-level entities for the organization and the relationship among those entities An enterprise data model – An entity is an object or concept that is important to the business – ERD Relational Databases – ORDER (O_ID, C_ID, O_Date) – ORDER_LINE (O_ID, P_ID, QTY_Ordered) A database application is used to perform a series of database activities (create, read, update, delete) – The range of Database ApplicationsDatabase Applications Advantages

Segment from enterprise data model

One customer may place many orders, but each order is placed by a single customer  One-to-many relationship

Segment from enterprise data model One order has many order lines; each order line is associated with a single order  One-to-many relationship

Segment from enterprise data model One product can be in many order lines, each order line refers to a single product  One-to-many relationship

Segment from enterprise data model Therefore, one order involves many products and one product is involved in many orders  Many-to-many relationship

Order and Order_Line tables

Product and Customer tables

Figure 1-4 Order, Order_Line, Customer, and Product tables Relationships established in special columns that provide links between tables

Figure 1-5 Client/server system for Pine Valley Furniture Company

Advantages of the Database Approach Data Independence/Reduced Maintenance – Data independence refers to the separation of data descriptions from the application programs that use the data Improved Data Sharing Increased Application Development Productivity Enforcement of Standards Improved Data Quality (Constraints) Better Data Accessibility/ Responsiveness Security, Backup/Recovery, Concurrency

The Range of Database Applications Personal Databases – support one user Workgroup Databases – a workgroup is a relatively small team of people who collaborate on the same project or application Department Databases – support the various functions and activities of a department Enterprise Databases – ERP work with the current operational data – Data warehouses Internet Databases

Workgroup database

Figure 1-9 An enterprise data warehouse

Components of the Database Environment CASE Tools Repository - a centralized storehouse for all data definitions, data relationships, and other system components Database Management System (DBMS) Database - organized collection of logically related data Application Programs User Interface Data Administrators System Developers End Users

Components of the Database Environment

Evolution of Database Technologies

Evolution of DB Systems Flat files s s Hierarchical – 1970s s Network – 1970s s Relational – 1980s - present Object-oriented – 1990s - present Object-relational – 1990s - present Data warehousing – 1980s - present Web-enabled – 1990s - present

Figure 1-2 Three file processing systems at Pine Valley Furniture Duplicate Data

Problems with Data Redundancy Waste of space to have duplicate data Causes more maintenance headaches The biggest Problem: – When data changes in one file, could cause inconsistencies – Compromises data integrity

Problems with Data Dependency  Each application programmer must maintain their own data  Each application program needs to include code for the metadata of each file  Each application program must have its own processing routines for reading, inserting, updating and deleting data  Lack of coordination and central control  Non-standard file formats

Costs & Risks of the Database Approach Up-front costs: – Installation Management Cost and Complexity – Conversion Costs Ongoing Costs – Requires New, Specialized Personnel – Need for Explicit Backup and Recovery Organizational Conflict – Old habits die hard