COM206 Database Systems Quiz

Study Notes

A database is a collection of data, with descriptions of the data types, structures, and constraints, stored in a database catalog or dictionary (meta-data).
The database definition involves specifying the data types, structures, and constraints of the data to be stored.

Defining a database involves specifying the data types, structures, and constraints of the data to be stored.
Constructing a database involves storing the data on some storage medium controlled by the DBMS.
Manipulating a database includes querying, updating, and generating reports.
Sharing a database allows multiple users and programs to access the database simultaneously.

An application program accesses the database by sending queries or requests for data to the DBMS.
A query causes some data to be retrieved.
A transaction may cause some data to be read and some data to be written into the database.

Protection includes system protection against hardware or software malfunction and security protection against unauthorized access.

Program data dependence: programs maintain metadata for each file they use.
Duplication of data: different systems/programs have separate copies of the same data.
Limited data sharing: no centralized control of data.
Lengthy development times: programmers must design their own file formats.
Excessive program maintenance: 80% of information systems budget.

Central repository of shared data.
Data is managed by a controlling agent and stored in a standardized, convenient form.
Self-describing nature of a database system: a DBMS catalog stores the description of a particular database.
Insulation between programs and data: program-data independence.
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.
Sharing of data and multi-user transaction processing.

Actors on the scene: those who use and control the database content.
- Database administrators: authorize access, coordinate and monitor use, acquire software and hardware resources.
- Database designers: define the content, structure, and constraints of the database.
- End-users: use the data for queries, reports, and updates.
Workers behind the scene: those who design, develop, and maintain the DBMS software and related tools.
- System analysts and application developers: understand user requirements, design applications, and implement specifications.
- Business analysts: analyze vast amounts of business data for better decision making.
- System designers and implementers: design and implement DBMS packages.
- Tool developers: design and implement software systems for modeling, designing, and using databases.
- Operators and maintenance personnel: manage the actual running and maintenance of the database system hardware and software environment.

Controlling redundancy in data storage and development efforts.
Sharing of data among multiple users.
Restricting unauthorized access to data.
Providing persistent storage for program objects.
Providing storage structures for efficient query processing.
Providing optimization of queries for efficient processing.
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 from the stored data using deductive and active rules and triggers.