The product that was nowhere
An order says product SK-0472 was sold. The catalogue has no SK-0472. It has SK-0427.
Two digits were swapped. The sales report is wrong, and the stock count is wrong too. Six checks can stop this kind of fault. This lesson covers all six.
Key words
| Word | What it means | Example |
|---|---|---|
| Validation | A check that data is sensible and in the right shape. | A code must be SK- and four digits. |
| Verification | A check that data was copied or typed in correctly. | Type the code twice. |
| Reliability | Data you can depend on, from a trusted source. | The head office catalogue |
| Consistency | The same fact matching everywhere it is kept. | One code, two lists, no difference |
| Integrity | Data that stays complete, correct and properly linked. | An order points to a real product. |
| Redundancy | The same data kept more than once when it is not needed. | The same product listed twice |
| Record | One row of data about one thing. | SK-0427, Notebook |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can name six checks that keep data good and say what each one does.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Validation and verification
Validation asks: is this sensible? The computer checks the shape and the range of data as it goes in. A code with 3 digits is refused.
Verification asks: was this copied correctly? The person types the code twice, and the computer checks both match. A code can be valid and still be the wrong code.
Reliability and consistency
Reliability is about the source. Data from the official catalogue is more reliable than a note on a sticky label.
Consistency is about agreement. If two lists hold the same product, both must give the same price. When they differ, nobody knows which is right.
Integrity and redundancy
Integrity means data stays complete, correct and linked. An order must point to a product that exists. If the product is deleted, the order has a broken link.
Redundancy is needless repeats. The same product listed twice wastes space and can disagree with itself. A planned backup copy is a good copy. A careless duplicate is not.
Check: which method?
Have a go
Check: which method?
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.