For example : The risk to soil erosion is low if the slope is gentle and the soil depth is shallow and the the rock is permeable

or

the slope is medium and the soil depth is deep and the rock is permeable.

What is then the value of the membership function of field A to class "low risk" to soil erosion?

When several links act together in parallel, the strength of the overall link is as strong as the strongest of the individual links.

This is a case on disjunctive reasoning, where more than one alternative routes may lead to the same conclusion.

In the example depicted above, the chain at the top is as strong as its weakest link, i.e., it has strength 0.3. The chain at the bottom is also as strong as its weakest link, so its strength is 0.4. So, the strongest of the two parallel chains is the bottom one with strength 0.4, and this is the strength with which we associate field A with the class "low risk" to soil erosion.

 

 

Click here to find out the drawbacks of these rules of reasoning