Digital Solutions External

Synchronous Data Exchange

the sender and receiver take turns sending and acknowledging data exchanges

Asynchronous Data Exchange

the sender sends data but does not wait for a response

REST

Representational State Transfer. Set of rules for building web applications/APIs. Stateless - The server provides whatever information the client needs to interact with the service. 

API

data exchange application that enables two software components to communicate with each other using a set of definitions and protocols. Request → API → Server → API → Client

API Key

Unique code provided to a user which identifies them and authenticates their use of an API. Used to control and track an API’s usage.

JSON

Javascript Object Notation. Language used by API’s. Does not use end tags. Shorter and quicker to read and write. Easier to parse values.

{"employees":[ 
  { "firstName":"John", "lastName":"Doe" }, 
]} 

XML

Similar to HTML. All elements must be closed, no built-in tags. Easily readable but requires an XML parser.

<employees> 
  <employee> 
    <firstName>John</firstName> <lastName>Doe</lastName> 
  </employee> 

Latency

delay between the time an application requests data and the time it receives data. influenced by serialisation, propagation, switching and queuing

Jitter

irregular latency in data transmission (lag/stuttering) caused by irregular packet transmission and network congestion. Often noticeable in synchronous exchanges.

Guarantee

promise to that all data packets will be received and in the correct order during data delivery. Essential for applications where data accuracy is critical, such as file transfers and financial transactions.  

Timeliness

timeliness of delivery - how current a data packet is at the time it is received. If a packet takes too long to arrive, it can be discarded.

Best-Effort Services

no guarantee of timeliness

Differentiated Services

traffic that is given priority to reduce latency or variance in packet delay

Guaranteed Services

uses network bandwidth reserved for critical applications 

Network Transmission Principles

Steps that must be completed when data is sent between two networked devices

Streaming and Broadcasting Data Packets

1. Data is packaged and addressed

2. Data is serialised into bits, and each bit is sent one at a time

3. Each bit travels through physical cable or airwaves to the nearest connected device

4. The nearest connected byte collects the bits and checks each byte arrived safely using a checksum. It then sends the data bit by bit to the next device.

5. At particular points during the transmission, a router inspects the data packet to determine the next nearest network device to transmit the package to

6. This continues until packets begin to arrive at their intended location

7. As each packet arrives, it is checked for corruption using a checksum. If it is corrupted or lost, a replacement packet is requested

8. Packets are buffered in memory until all packets have arrived

9. Once all packets have been received, they are re-assembled

10. Additional protocols may be performed to check the data’s integrity and authenticity

Network Transmission Protocols

rules that define the exchange of data packets between two or more servers/devices over a network e.g. mechanisms for device identification and establishing connections between devices, formatting rules about how data packets are structured and sent/received, rules about message recognition and data compression

Communication Protocols

Determine rules and formats to transfer data across networks. Relate to syntax, authentication, semantics, and error detection e.g. HTTP, HTTPS, FTP, VPN

HTTP

Hyper-text Transfer Protocol. Protocol of the internet that allows communication between a server and client. Stateless. Client sends HTTP request, HTTP server responds to request. Request contains a method type (GET/POST/ PUT/DELETE) and URI (Uniform Resource Identifier). Response contains success or error code and messages containing requested data

HTTPS

Secure version of HTTPS. Uses Transport Layer Security (TLS) or Secure Socket Layer (SSL) to encrypt transmission using public key encryption methods.

Sequence

a series of steps or instructions that follow one after the other

Iteration

using loops to avoid having to repeat unnecessary code. Includes for while and do while loops.

Condition

logical expression that is true or false

Selection

Choosing whether code should run or not based on a condition e.g. if statement

Functions

Used to define a sequence of code by a name, that can be called by other code. Used to avoid repeating code.

Variables/Assignment

Containers that store (remember) data so it can be used elsewhere

Modularisation

Reducing a systems complexity by breaking it up into units/modules

Substitution Cipher

The sender encrypts the message and sends it to a receiver. Receiver deciphers the text by doing the opposite of encryption process.

Caesar cipher

simple substitution cipher. each letter is shifted by a constant amount.

Polyalphabetic Cipher

Substitution cipher where the amount each letter has shifted by changes over the course of the message

Vigenere Cipher

A random keyword is created and repeated to match the length of the message. Each letter in the message is shifted by the numerical value of its corresponding letter in the keyword or a cipher table can be used.

Gronsfeld Cipher

Uses a numeric key, repeated to match length of message. Each letter in the message is shifted by its corresponding numerical value.

One-Time Pad Encryption

A unique key the length of the message is randomly generated. Both the sender and recipient have a copy of this key. Each letter is shifted by the numerical value of its corresponding letter in the key. To decrypt, the receiver shifts the letters back using the key.

Elements of Visual Communication

Line, space, colour, shape, tone, texture, form, scale, proportion

Principles of Visual Communication

Hierarchy, balance, contrast, alignment, proximity, harmony, repetition

Accessibility

Ability to be used by many different people, including those with disabilities

Effectiveness

Ability of users to use the system to do the work they need to do, includes reliability

Utility

Ability of the system to provide all the functionality that users need

Safety

Ability for users to make mistakes and recover from them

Learnability

How easy a system is to learn

APP 1

Personal information must be managed in an open and transparent way. Have a clearly expressed and up to date privacy policy.

APP 2

Individuals should have the option of not identifying themselves or using a pseudonym unless the entity is required or authorised by law to deal with identified individuals

APP 3

Agencies and organisations can only solicit and collect personal information that is reasonably necessary and from the individual concerned and it must be collected lawfully and fairly.

APP 4

Most unsolicited personal information must be destroyed or de-identified ASAP unless it is from a Commonwealth record. If the agency/organisation is not required to destroy the information, they can manage it using APPS 5-13

APP 5

An organisation that collects personal information about an individual must notify the individual that certain information has been collected, before or at the time of collection. They should also inform them the purposes of collection, the privacy policy, and consequences if information is not collected.

APP 6

Organisation can only use or disclose personal information for the reason it was collected

APP 7

An organisation must not use or disclose personal information it holds for the purpose of direct marketing.

APP 8

Before an organisation discloses personal information to an overseas recipient, they must ensure that the overseas recipient does not breach the APPs in relation to the information

APP 9

An organisation should not use a government related identifier as its own identifier of an individual unless an exception applies

APP 10

Personal information should be accurate, up-to-date, and complete

APP 11

An organisation must protect personal information from misuse, interference, and loss. They should also protect against unauthorised access, modification, or disclosure.

APP 12

If an organisation stores personal information, they must give the individual access to their personal information if requested

APP 13

Organisations should correct personal information that is not accurate, up to date, complete, relevant or misleading

%

for zero of more unknown characters

_

for a single unknown character

LIKE

used for partial matching

IN

allows you to specify multiple conditions in a where statement

HAVING

WHERE for calculation functions

GROUP BY

used with calculation functions to group results by a condition

inner-join

uses a matching field to select data from multiple tables

create a database

CREATE TABLE users (

uid integer unsigned auto_increment not null,

uname varchar(100) not null,

primary key (uid)

);

delete a table

DROP TABLE table_name;

add/delete/modify columns in an existing table

ALTER TABLE table_name

ADD column_name datatype;

DROP COLUMN column_name;

RENAME COLUMN old_name to new_name;

ALTER COLUMN column_name datatype;

add a new record to a table

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

modify an existing record in a table

UPDATE table_name
SET column1 = value1
WHERE condition;

delete existing records in a table

DELETE FROM table_name

WHERE condition;