CCEA A-Level Software Systems Development CL4
Software and the Development Environment
Defining Data: Types, Variables and Classes
Program Control Structures
Objects, Classes and Data Structures
Exception Handling and Managing Input and Output
Testing an Object Oriented Application
Graphical User Interface Objects and Events
Multiple Forms and Linking to Files
Designing, Testing and Evaluating an Event Driven Application
Reasons for Systems Development and Systems Methodologies
Managing Projects
Testing Strategies
Database Concepts and Entity Relationship Modelling
Normalisation and Structured Query Language
Project Management and the Systems Approach in Practice
Defining Requirements and Documenting the Design
Building a Desktop Solution with a Database
Testing and Evaluating the Solution
Database Concepts and Entity Relationship Modelling
What a database is and why one is used
- 3 things to know
- A2 Unit 1
Overview
Database management system, data redundancy and data inconsistency.
What you need to know
Answer each one before you reveal it.
What is a schema?
How does a database control who may see what?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a database?
Model answer
A database is an organised, persistent collection of related data held so that more than one application can use it, with the structure of the data defined separately from the programs that read and write it.
- 2
What is a database management system?
Model answer
A database management system is the software that creates and maintains the structure of a database, enforces its rules, controls who may see and change what, and processes queries and updates on behalf of applications.
- 3
Why is storing data in application files a poor arrangement?
Model answer
Each application defines its own file layout, so the same fact is stored separately by each of them. Storage is wasted, an update applied to one file and not another leaves them contradicting each other, and no application can answer a question that spans two of the files.
- 4
What is data redundancy?
Model answer
Data redundancy is the storage of the same item of data in more than one place. Redundancy wastes space and, more importantly, creates the opportunity for the copies to disagree.
- 5
What is data inconsistency?
Model answer
Data inconsistency is the state in which two stored copies of the same fact disagree, because one was updated and the other was not. Redundancy is the cause and inconsistency is the consequence.
- 6
What is meant by data integrity?
Model answer
Data integrity is the accuracy and internal consistency of the stored data over its whole life, maintained by validation on entry, by rules linking one table to another, and by controls that prevent unauthorised or partial change.
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