The perceptions system is entirely based on Stimuli emission by Entities and on receiving of these Stimuli by other Entities.
There are two kinds of Stimuli. We can distinguish:
Description (or state) Stimuli which describe the state of the associated Entity. These Stimuli can last an infinite time.
Example 1. Description Stimuli duration
The torch is giving out light: 6 hours duration.
The flag is red: infinite duration.
Action Stimuli describe actions of associated Entities. Their duration is instantaneous.
Example 2. Action Stimuli
Janselmeer lights the torch.
The torch goes out.
The dragon utters a deafening growl.
a means of effecting or conveying something (Merriam-Webster's Collegiate Dictionary)
channel for the transmission of some Stimuli: only Stimuli corresponding to the medium can be transmitted by this medium.
Stimuli can also have multiple shapes and intensities. A Stimulus can thus go down the following Media:
Visible light
Infrared
Ultraviolet
Sound
Infra-sound
Ultrasound
Mechanic (touch)
Flavour (taste)
Smell
Magnetic field
Electric field
Life
Magic
Invisible
Telepathy
Feeling (to feel real feelings of somebody)
...
Its intensity is given by a positive real number. A value of 1 means a normal (or medium) intensity. Below 1, intensity is low. Above 1, intensity is high.
A scale can be built by applying a decimal logarithm:
<0.001 -> <-3: exceptionally weak intensity. 0.001 -> -3: very weak intensity. 0.01 -> -2: weak intensity. 0.1 -> -1: low intensity. 1 -> 0: medium intensity. 10 -> 1: high intensity. 100 -> 2: strong intensity. 1000 -> 3: very strong intensity. >1000 -> >3: exceptionally strong intensity.