Unit 4 - Exchanging Data

Question 1

Why use compression?

Answer 1

Reduce the storage space of files on disk

Makes transferring data and sharing data easy

Question 2

Lossy compression

Answer 2

Works by removing non-essential information. But one has been heavily compressed, display untidy and blocky compression artefacts as a consequence. Compresses at the cost of quality.

Question 3

Lossless compression

Answer 3

Works by recording patterns in data rather than the actual data. Using these patterns and a set of instructions and a set of instructions on how to use them. Groups similar pieces of information together. Much larger file than the lossy but still significantly less than the original.

Question 4

Encryption.

Answer 4

Encryption is the transformation of data from one form to another to prevent an unauthorised third party. The original message is known as plaintext. The encrypted data is known as ciphertext. The encryption method or algorithm is known as the cypher, and the secret information to lock or unlock the message is known as a key.

Question 5

Hashing

Answer 5

A function provides a mapping between an arbitrary length input and a usually fixed length or smaller output. Unlike the encryption techniques, you can’t go back to the original.

Question 6

Normalization

Answer 6

No data is unnecessarily duplicated.
Data is consistent throghout the database a costumer is not recorded as having different addresses in different tables.
The structure of each table is flexible enough to allow you to enter as many or as few items as required.
The structure should enable a user to make all kinds of complex queries testing data from different tables

Question 7

First normal form

Answer 7

First normal form (1NF) if it contains no repeating attribute of groups and attributes

Question 8

Modelling data requirements

Answer 8

Consists of a single file. It might be a suitable structure to hold the name and address of all components.