Data and Information Sources

Data and Information

• Data is raw, meaningless numbers, letters, symbols, sounds, or images without context
• Information is data with context and meaning

Data Sources

• Direct data sources collect data for a specific purpose, used by the collector
• Surveys of customers who purchased trainers from other shops are also considered indirect sources, with prices potentially discounted or changed
• Visiting other shops and noting prices or visiting websites to note prices are ways of using direct sources
• Indirect data sources use data collected for a different purpose
• Electoral registers contain names and addresses, aiding election processes
• Credit reference agencies use electoral registers to verify addresses; marketing agencies use them for direct marketing, with options to hide entries from public view
• Businesses purchase email lists or phone numbers for marketing, enabling targeted campaigns like IT textbook sales to IT teachers

Data Source Examples

• Names and email addresses of a political party member are collected so the party can contact them; they are then used to ask for donations
• Employee attendance dates/times are collected to calculate wages; they are then used to check an employee's alibi

Direct Data Sources

• Data relevance is high
• Original source is known and trustworthy
• Data is generally up-to-date
• Bias can be eliminated through specific questions
• Data format can be customized

Indirect Data Sources

• Data is immediately available
• Large samples enable statistical analysis
• Data may be outdated
• Original source might be biased
• Data format may be unsuitable, complicating extraction

Quality of Information: Overview

• Data must be accurate for good quality, for example a decimal point must be in the correct place
• Relevance is key; unnecessary information complicates the search for what is needed
• Information should be up-to-date, otherwise it isn't useful

Level of Detail

• Good quality information has the right amount of detail
• Completeness involves providing all necessary information for usability

Encryption

• Scrambles data, rendering it unreadable without a decryption key
• The purpose of it is to make data unreadable if an unauthorised user intercepts it

Why Encrypt?

• Encryption is important, as data stored on disks can be stolen/lost
• Data transmitted over networks can be intercepted by hackers

Caesar Cipher

• Ciphers convert text messages into encrypted messages
• It is a shift cipher and it replaces letters by shifting along the alphabet
• Using a shift of +3, "Hello" becomes "KHOOR"

Symmetric Encryption

• It requires sender and recipient to have a private encryption/decryption key that must be transmitted, making it interceptable

Asymmetric Encryption

• Public-key cryptography includes a public key available to anyone and a private key only known to the recipient
• Digital certificates help find the public key, identifying the user/server
• During encryption, the computer requests the digital certificate, which contains the public key
• It is used for SSL/TLS providing security for websites and it requires more processing power
• It is more secure, as the decryption key does not need transmission

Asymmetric Encryption Applications: Hard Disk

• Encryption of every bit of data on a disk using specialized software
• Benefit: automatic encryption on saving
• If the OS becomes corrupted, all data is lost permanently
• Encryption keys must be in a safe place
• Booting up the computer is slower

Single File Encryption

• This process requires the encryption key
• USBs and backup tapes should be encrypted
• Data is accessed by entering a password or a fingerprint

Applications: HTTPS

• Hypertext Transfer Protocol Secure (HTTPS) encrypts sensitive data (e.g., credit card numbers) on web pages using SSL/TLS
• Banks use TLS when users log onto online banking
• A secure page starts with "https://" and has a padlock symbol
• When a browser requests a secure page, it checks the digital certificate
• The browser uses the public key to encrypt a new symmetric key and send it to the web server
• The browser and server talk through symmetric encryption, which is faster

Applications: Email

• Achieved through public key cryptography/asymmetric encryption
• The recipient has to use a private key
• The sender and recipient have to send each other digitally-signed messages
• Encrypting an email also encrypts its attachments

How Encryption Protects Data

• Encryption protects data by scrambling it
• 256-bit AES encryption makes it virtually impossible to decrypt data, effectively protecting it

Data Validation

• Validation ensures data matches acceptable rules
• Presence Check: if the data hasn't been entered then the user is asked to enter data
• Range Check: To ensure that data is within a defined range
• Limit Check: Has a single boundary as the highest possible value or the lowest possible value

Type check

• A type check ensures that data must be of a defined data type
• Example of type check is to enter an age as an integer

Length check

• It ensures data is of a defined length or within a range of lengths
• For example it could be used to set a password

Checking data accuracy methods

Format check

• A format check ensures that data matches a defined format or pattern. For example, a student ID may need four numbers followed by two letters

Lookup check

• A lookup check tests to see if data exists, for example only 'X', 'P', 'M' or 'D' are entered

Consistency check

• A way to compare data in one field with data in another field that already exists within a record, to see whether both are consistent with each other
• For example, products scheduled to be dispatched can't be marked without packaging first

Check Digit

• A number/letter added to the end/beginning of a code to ensure the data is accurate
• The number is input then and algorithm is run to validate it

Data Verification

• Involves checking that the data entered into the computer system matches the original source
• Visual checking allows a user to visually check that the data entered matches the original source. done by the user

Double Data Entry

• This is where data the entered twice and compared, and if the data is different then the data must have been entered wrong the first time

Hash Total

• Used when inputting a set of data. It is calculated by adding together values from an input field
• Before input, the user manually adds up the values
• Post-input, the computer calculates the total for comparison

Control Total

• Very similar to a has total, as data is also summed, but the figures inputted have meaning

Parity Check

• It is used to find errors during data transmission.
• There are two types of parity check: either "even parity" or "odd parity."

Checksum

• They are a follow-on from the use of parity checks in that they are used to check that data/contents of a file has been transmitted accurately

Important note on validation

• It is possible to enter valid data that is still incorrect. For example verifying incorrect data
• By using both validation and verification, the chances of entering incorrect data are reduced

Data Processing

• Data processing is any activity that manipulates or carries out operations on data.
• Includes actions like collection/storage, editing, sorting, output

Batch Processing

• Batch Processing collects individual operations/. transactions that need to be performed on the data together into a batch
• Examples of where batch processing can be used is on automated backups and in the processing of wages or stock control

Files

• Master file - Used to store data for examples customers personal information

Transaction File

• A file where product order data is recorded

Algorithm example of the process

• At the start of the process, the transaction file is validated and any transactions that are invalid will be moved to an errors file
• The transaction file is sorted so that it is in the same order as the master file

Batch Processing: Advantages

• Single, automated process reduces human costs
• Can be scheduled during low-demand times
• Reduces transcription/update errors
• Fewer repetitive tasks for humans

Batch Processing: Disadvantages

• Data processing is delayed until a specific time period.
• Only data of the same type can be processed since an identical, automated process is being applied to all the data.
• Errors can't be corrected until the batch is complete

Automation example

• We can give each type of update a letter. • Changing an existing record in the master file will be C • Deleting a record from the master file will be D • Adding a new record to the master file will be A

Online data processing

• A real-time system uses a feedback loop to process inputs and generate outputs immediately
• System data flow requires feedback to monitor something like data temperature

Real Time: Example algorithm

• The system would have to go through each transaction file record and using the hourly rate (Rate) from the matching master file record, calculate that employee's wages for the week. This would be added to the employee's wages paid so far this year and replace the Wages_to_date value

Electronic Funds Transfer (EFT)

• It's the electronic transfer of funds to or from a bank account
• Direct payments enable bank-to-bank transfers
• ATMs allow cash withdrawals
• Debit cards facilitate payments for goods/services
• Direct debits authorize regular payments automatically

Online purchases: Example algorithm

• Log on by entering username and password
• Select card type, enter the card number
• An email address can be used notify the customer, and a delivery can be used so the store knows where the goods will be sent to

Automatic Stock control

• To ensure that shop always has enough stock, a database is needed
• The computer searches for this barcode number, it looks up the re-order quantity of that product and sends the order automatically to the supplier using the supplier's contact details

Electronic Data Exchange

• It is a standardised format for exchanging data between organisations
• Application Program Interfaces (APIs) are used to provide a standard interface for importing and exporting data between different software.

EDI usage example

• the buyer can create a purchase order, the software will transmit the order using EDI directly to the supplier's ordering system. the supplier can create an electronic invoice which will be transmitted by their software to the buyer's software

Real Time Feedback Example

• A central heating system that is constantly monitoring the temperature of its surroundings

algorithm example

• the boiler is switched off by the microprocessor, which then results in a drop in temperature and the boiler has to come back on again and so the sequence is repeated
• This requires input from a pre-set, and an on/off switch

Algorithm variation example

• It is more sophisticated than central-heating systems and involve units such as valves, compressors, condensing units and evaporating units, which together form a system