Week 1B - More info on DBs

Question 1

What is the primary characteristic of the database approach regarding data storage?

Answer 1

A SINGLE repository of data that is defined once, maintained centrally, and accessed by multiple users.

Question 2

What makes a database “self-describing”?

Answer 2

The database contains both the actual data AND descriptions of database structures/constraints (metadata) stored in the data dictionary/catalog.

Question 3

What is “data abstraction” in database systems?

Answer 3

The conceptual representation of data that hides storage details and implementation.
It operates through three levels.

Question 4

Data abstraction operates through three levels. These are?

Answer 4

1) External schema (user view)
2) Conceptual schema (logical structure)
3) Physical schema (storage details)

Question 5

What is meant by “insulation between programs and data”?

Answer 5

Program-data independence means applications don’t need to be modified when the physical data storage structure changes.

Question 6

What is a database “view” and why is it important?

Answer 6

A view is a user-specific subset of the database that:
- Shows only relevant data for specific users
- Is virtual/dynamic (not explicitly stored)
- Provides additional security and data abstraction

Question 7

What are the key features of multi-user transaction processing?

Answer 7

1. Concurrency control for simultaneous access
2. Online transaction processing (OLTP)
3. Ability to share data safely between use

Question 8

What are the main types of data models mentioned?

Answer 8

1. Relational data model
2. Object-oriented data model
3. Entity-relationship model (ERM)
4. Unstructured/semi-structured data models

Question 9

Why is the DBMS software considered “general-purpose”?

Answer 9

It works with any number of database applications rather than being specific to one business domain or application.

Question 10

Who are the main actors in day-to-day database use?

Answer 10

1. Database Administrators (DBA)
2. End-users (casual, naïve/parametric, sophisticated)
3. Database designers/architects
4. System analysts and application programmers

Question 11

How does a DBMS help control redundancy?

Answer 11

It reduces:
- Duplication of effort
- Wasted storage space
- Data inconsistency

Question 12

What security advantage does a DBMS provide?

Answer 12

Controls/restricts unauthorized access through privileged software (DBA can create user accounts)

Question 13

How does DBMS handle program objects and data structures?

Answer 13

Provides persistent storage, eliminating need for conversion between file and objects

Question 14

What are the two types of rules a DBMS can use?

Answer 14

1. Deductive rules (infer new information from stored data)
2. Active rules (automatically initiate actions)

Question 15

What 6 user interfaces does a DBMS typically provide?

Answer 15

1. Query language for casual users
2. Programming language interface
3. Forms and command codes
4. Menu-driven interface
5. Web access
6. Query generation tools

Question 16

How does a DBMS enforce data integrity?

Answer 16

1. Enforces data type constraints
2. Maintains relationships between files
3. Ensures uniqueness of values
4. Provides automatic enforcement
5. Validates during data entry

Question 17

What are the main reasons to NOT use a DBMS?

Answer 17

1. Unnecessary overhead costs (security, concurrency, recovery)
2. Simple, well-defined applications unlikely to change
3. Vague requirements/prototyping phase
4. Real-time requirements that can’t handle overhead
5. No need for multi-user access

Question 18

What are the business advantages of using a DBMS?

Answer 18

1. Enforces standards
2. Reduces application development time
3. Provides flexibility for changing requirements
4. Ensures up-to-date information
5. Creates economies of scale

Question 19

Why does using a DBMS reduce application development time?

Answer 19

Applications can focus on business logic while outsourcing data-related issues to DBMS