1.3 Revision

Entity

An item of interest about which information is stored

Relational Database

A database that recognizes the differences and similarities between entities and creates different tables for each entity.

Flat File Database

Database that consists of one file, based around a single entity and its attributes

Foreign Key

Attribute linking two tables together. Exists as primary key in one, and foreign key in the other

Primary Key

Unique identifier for each record in the table.

Capturing Data

The method of actually inputting data into a database

Manual Entry

Manually entering information about something into a database

Magnetic Ink Character Recognition

Details printed in magnetic ink that’s recognized by the computer, entered into the database

Optical Mark Recognition

Recognizes marks such as dashes, crosses or circles, and inputs into database.

Selecting Data

Choosing data that meets a certain criteria to reduce volume of input

Exchanging Data

Transferring data, commonly through Electronic Data Interchange, data transfer from computer to computer

Network

Name given to two or more computer connected to each other with the ability to transmit data between each other

LAN

Local Area Network, a network spread over a small geographical area, e.g. office or school

WAN

Wide Area Network, network spread over large geographical area, such as a network of multiple offices.

Protocols

Set of rules defining how devices should communicate with each other. They are standard to all devices can communicate with each other, regardless of manufacturer.

TCP/IP Stack: Application

Specifies what protocol should be used in relation to the application being used

TCP/IP Stack Transport

Establishes end-to-end connection between sender and receiver. Splits data up into packets and can request retransmissions

TCP/IP Stack Network

Adds the source and destination IP addresses

TCP/IP Stack Link

Adds the MAC address and identifying NICs of source and destination computers.

Domain Name System

System used to organize internet resources. Includes names instead of IP addresses that the user would not be able to remember.

Data Packet

Segments of data that have been broken down and make up full data

Header

Sender and Recipient IP addresses. Protocol being used. Order of packets.

Payload

Raw data being transmitted

Trailer

Checksum, which detects if there were any errors during transmission

Packet Switching

A method of communication in which packets are transmitted across a networks, taking the most efficient route, which varies for each packet

Packet Switching Pros

Methods to ensure data arrives intact, Multiple routes can be used, Packets can be transferred over large networks

Packet Switching Cons

Time is spent deconstructing and reconstructing data packets. Must wait for all packets to arrive before data can be received

Circuit Switching

Direct link is created between two devices, which is maintained for the duration of the conversation. Requires devices to operate at the same rate.

Circuit Switching Pros

Data arrives in logical order. Enables two users to hold a call without delay in speech.

Circuit Switching Cons

Bandwidth is wasted when no data is sent. Devices must operate at the same rate. If one path fails, the entire data is lost and must be resent.

Client-server

Network consisting of terminals connected to a server which is a central computer. Server holds all important information and resources. Handles requests from clients

Client-server Pros

More secure as data is one location. Allows for central backups. Data and resources can be shared between clients

Client-server Cons

Relatively expensive to set up. Single point of failure; if server fails, entire network fails. Trained staff required to maintain the server

Peer-to-peer

Network in which computers are connected to each other so they can share data. Each device acts as a server and a client, providing requests and responses

Peer-to-peer Pros

Cheaper to set up. Allows resources to be shared. Easy to maintain. No single point of failure

Peer-to-peer Cons

Backups must be performed separately. Poorer security.

Lossy Compression

Compression method that reduces the file size whilst also removing some information

Lossy compression Pros

Results in a significantly reduced file size.

Lossy Compression Cons

Data is lost when file is compressed and cannot be retrieved. Slightly reduces quality.

Lossless compression

Compression method that reduces file size without losing any informationL

Lossless Compression Pros

None of the original data is lost. Original file can be restored.

Lossless compression Cons

Reduced file size is not as small as lossy compression, so transfer may not be as efficient