Types of Databases (5)
- Numeric and Textual Databases
- Multimedia Databases
- Geographic Information Systems (GIS)
- Data Warehouses
- Real-time and Active Databases
Database Definition
A collection of related data.
Data Definition
Known facts that can be recorded and have an implicit
meaning.
Mini-world Definition
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) Definition
A software package designed to create and manage computerized databases.
Database System Definition
The DBMS software together with the data itself. Sometimes, the applications are also included.
DBMS Functionality (6)
- Define a database: in terms of data types, structures and
constraints - Construct or Load the database on a secondary storage medium
- Manipulate 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 - Protection or Security measures to prevent unauthorized access
- Visualization of data
Self-Describing Nature of a Database System (Characteristic of a DB)
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 (Characteristic of a DB)
Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs.
Data Abstraction (Characteristic of a DB)
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 (Characteristic of a DB)
Each user may see a different view of the database, which describes only the data of interest to that user.
Sharing of Data and Multi-user Transaction Processing (Characteristic of a DB)
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 (3)
- 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 endusers 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 (4)
- Casual: Access database occasionally when needed
- Naïve or Parametric: They make up a large section of the enduser 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.
- 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 to using the Database approach (3)
- Sharing data among multiple users.
- Restricting unauthorized access to data.
- Controlling redundancy in data storage and in development and maintenance efforts.
Main inhibitors (cost) of using a DBMS (2)
- High initial investment and possible need for additional hardware.
- Overhead for providing generality, security, concurrency control, recovery, and integrity functions.
When a DBMS may be unnecessary (3)
- If the database and applications are simple, well defined, and not expected to change.
- If there are stringent real-time requirements that may not be met because of DBMS overhead.
- If access to data by multiple users is not required.
