Module 19 ยท What do the logic symbols mean?
The five symbols CNA speaks in
By the end of this module you will be able to
- Read the five core CNA symbols.
- Tell AND (*) from OR (+) in a formula.
- Recognise that lower-case means absence.
Every CNA formula is built from a tiny vocabulary. Learn these five and you can read any solution the package ever hands you.
| Symbol | Means | In plain words |
|---|---|---|
| * | AND | both conditions must be present together |
| + | OR | either road will do on its own |
| <-> | equivalence | the left side tracks the outcome exactly |
| -> | sufficiency | the left side is enough for the right |
| a | absence | lower-case means that condition is absent (0) |
So a formula like NoCold*NoComm + NoSuper would read: "(broken cold chain AND no mobilisation) OR (no supervision)." That single line captures both conjunctivity, the *, and equifinality, the +, at the same time. Two ideas, one tidy line.
Reflect
Practise on a formula of your own.
- Can you point to the conjunctivity (*) and the equifinality (+) in it?
- What would the same formula mean if one term were lower-case?