CONTENTS
1. Introduction to Database and Examples
2. Characteristics of Data Base approach
3. DB Users
4. Advantages of DBMS Approach
5. Disadvantages of DBMS Approach
Types of Databases and Database Applications
Numeric and Textual Databases
Multimedia Databases
Geographic Information Systems (GIS)
Real-time and Active Databases
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.
Typical DBMS Functionality
Define a database : in terms of data types, structures and constraints
Construct or Load the Database on a secondary storage medium
Manipulating the database : querying, generating reports, insertions, deletions and modifications to its content
Concurrent Processing and Sharing by a set of users and programs – yet, keeping all data valid and consistent
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
Example of a Database
Mini-world for the example: Part of a UNIVERSITY environment.
Some mini-world entities:
STUDENTs
COURSEs
SECTIONs (of COURSEs)
(academic) DEPARTMENTs
INSTRUCTORs
.
Example of a Database
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
Main Characteristics of the Database Approach
Self-describing nature of a database system: A DBMS catalog stores the description of the database. The description is called meta-data). This allows the DBMS software to work with different databases.
Insulation between programs and data: Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs.
Main Characteristics of the Database Approach
Data Abstraction: A data model is used to hide storage details and present the users with a conceptual view of the database.
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.
Main Characteristics of the Database Approach
Sharing of data and multiuser transaction processing : allowing a set of concurrent users to retrieve and to update the database. Concurrency control within the DBMS guarantees that each transaction is correctly executed or completely aborted. OLTP (Online Transaction Processing) is a major part of database applications.
Database Users
Users may be divided into those who actually use and control the content (called “Actors on the Scene”) and those who enable the database to be developed and the DBMS software to be designed and implemented (called “Workers Behind the Scene”).
Database Users
Actors on the scene
Database administrators: responsible for authorizing access to the database, for co-ordinating 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.
End-users: they use the data for queries, reports and some of them actually update the database content.
Categories of End-users
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.
Categories of End-users
Sophisticated : these include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities. Many use tools in the form of software packages that work closely with the stored database.
Stand-alone : mostly maintain personal databases using ready-to-use packaged applications. An example is a tax program user that creates his or her own internal database.
Advantages of Using the Database Approach
Controlling redundancy in data storage and in development and maintenence efforts.
Sharing of data among multiple users.
Restricting unauthorized access to data.
Providing persistent storage for program Objects (in Object-oriented DBMS
Providing Storage Structures for efficient Query Processing
Advantages of Using the Database Approach
Providing backup and recovery services.
Providing multiple interfaces to different classes of users.
Representing complex relationships among data.
Enforcing integrity constraints on the database.
Drawing Inferences and Actions using rules
Additional Implications of Using the Database Approach
Potential for enforcing standards: this is very crucial for the success of database applications in large organizations Standards refer to data item names, display formats, screens, report structures, meta-data (description of data) etc.
Reduced application development time: incremental time to add each new application is reduced.
Additional Implications of Using the Database Approach
Flexibility to change data structures: database structure may evolve as new requirements are defined.
Availability of up-to-date information – very important for on-line transaction systems such as airline, hotel, car reservations.
Economies of scale: by consolidating data and applications across departments wasteful overlap of resources and personnel can be avoided.
