Lakhasly

Introduction to Databases and Database Users

This chapter introduces databases and database users. It starts by discussing various types of databases, including traditional numeric and textual databases, multimedia databases, Geographic Information Systems (GIS), data warehouses, and real-time and active databases. The focus of the book, however, lies on traditional applications.

The chapter defines key terms like database, data, mini-world, Database Management System (DBMS), and database system. It then provides a simplified illustration of a database system environment.

Typical DBMS functionality includes defining database structure, loading initial data, manipulating data through queries and modifications, providing web access, and supporting concurrent user access while ensuring data consistency. Additional features include security measures, active processing, data visualization, and database maintenance.

An example using a UNIVERSITY environment demonstrates the concept of a mini-world with entities like students, courses, sections, departments, and instructors, and their relationships. The chapter also highlights key characteristics of the database approach, such as its self-describing nature, program-data independence, data abstraction, and support for multiple views of the data.

The chapter concludes by discussing different types of database users, categorizing them as those who use and control the database content ("Actors on the Scene") and those who design and develop the DBMS software and tools ("Workers Behind the Scene"). It further breaks down "Actors on the Scene" into database administrators, database designers, and end-users, emphasizing the importance of communication and understanding between these groups. Finally, it classifies end-users into casual, naïve, and parametric users, highlighting their varying levels of interaction with the database.

Chapter 1
Introduction: Databases and Database Users

Slide 1 - 3
Outline  Types of Databases and Database Applications  Basic Definitions  Typical DBMS Functionality  Example of a Database (UNIVERSITY)  Main Characteristics of the Database Approach  Database Users  Advantages of Using the Database Approach  When Not to Use Databases

Slide 1 - 4
Types of Databases and Database

Applications  Traditional Applications:  Numeric and Textual Databases  More Recent Applications:  Multimedia Databases  Geographic Information Systems (GIS)  Data Warehouses  Real - time and Active Databases  Many other applications  First part of book focuses on traditional applications

Slide 1 - 5
Basic Definitions  Database:  A collection of related data.  Data:  Known facts that can be recorded and have an implicit meaning.  Mini - world:  Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university.  Database Management System (DBMS):  A software package/ system to facilitate the creation and maintenance of a computerized database.  Database System:  The DBMS software together with the data itself. Sometimes, the applications are also included.
Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
Slide 1 - 6
Simplified database system environment

Slide 1 - 7
Typical DBMS Functionality  Define a particular database in terms of its data types, structures, and constraints  Construct or Load the initial database contents on a secondary storage medium  Manipulating the database:  Retrieval: Querying, generating reports  Modification: Insertions, deletions and updates to its content  Accessing the database through Web applications  Processing and Sharing by a set of concurrent users and application programs – yet, keeping all data valid and consistent

Slide 1 - 8
Typical DBMS Functionality  Other features:  Protection or Security measures to prevent unauthorized access  “Active” processing to take internal actions on data  Presentation and Visualization of data  Maintaining the database and associated programs over the lifetime of the database application  Called database, software, and system maintenance

Slide 1 - 9
Example of a Database (with a Conceptual Data Model)  Mini - world for the example:  Part of a UNIVERSITY environment.  Some mini - world entities :  STUDENTs  COURSEs  SECTIONs (of COURSEs)  (academic) DEPARTMENTs  INSTRUCTORs

Slide 1 - 10
Example of a Database (with a Conceptual Data Model)  Some mini - world relationships :  SECTIONs are of specific COURSEs  STUDENTs take SECTIONs  COURSEs have prerequisite COURSEs  INSTRUCTORs teach SECTIONs  COURSEs are offered by DEPARTMENTs  STUDENTs major in DEPARTMENTs  Note: The above entities and relationships are typically expressed in a conceptual data model, such as the

ENTITY - RELATIONSHIP data model (see Chapters 3, 4)

Slide 1 - 12
Main Characteristics of the Database

Approach  Self - describing nature of a database system:  A DBMS catalog stores the description of a particular database (e.g. data structures, types, and constraints)  The description is called meta - data .  This allows the DBMS software to work with different database applications.  Insulation between programs and data:  Called program - data independence .  Allows changing data structures and storage organization without having to change the DBMS access programs.

Slide 1 - 14
Main Characteristics of the Database

Approach (continued)  Data Abstraction:  A data model is used to hide storage details and present the users with a conceptual view of the database.  Programs refer to the data model constructs rather than data storage details  Support of multiple views of the data:  Each user may see a different view of the database, which describes only the data of interest to that user.

Slide 1 - 15
Main Characteristics of the Database

Approach (continued)  Sharing of data and multi - user transaction processing:  Allowing a set of concurrent users to retrieve from and to update the database.  Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted  Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database  OLTP (Online Transaction Processing) is a major part of database applications. This allows hundreds of concurrent transactions to execute per second.

Slide 1 - 16
Database Users  Users may be divided into  Those who actually use and control the database content, and those who design, develop and maintain database applications (called “Actors on the Scene”), and  Those who design and develop the DBMS software and related tools, and the computer systems operators (called “Workers Behind the

Scene”).

Slide 1 - 17
Database Users  Actors on the scene  Database administrators:  Responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software and hardware resources, controlling its use and monitoring efficiency of operations.  Database Designers:  Responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end - users and understand their needs.

Slide 1 - 18
Categories of End - users  Actors on the scene (continued)  End - users: They use the data for queries, reports and some of them update the database content.

End - users can be categorized into:  Casual : access database occasionally when needed  Naïve or Parametric: they make up a large section of the end - user population.  They use previously well - defined functions in the form of “canned transactions” against the database.  Examples are bank - tellers or reservation clerks who do this activity for an entire shift of operations.