The engineers understand the difference.
The aviators understand the difference.
But the attorneys... they are confused...
>>>> 1-12. USE OF WORDS SHALL, SHOULD, AND MAY. Within this technical manual the word “shall” is used to in- dicate a mandatory requirement. The word “should” is used to indicate a nonmandatory but preferred method of accomplishment. The word “may” is used to indicate an acceptable method of accomplishment. <<<<
http://www.tpub.com/content/aviationandaccessories/TM-1-1510-223-10/css/TM-1-1510-223-10_13.htm... why didn't those attorney legislators?
It seems that they were too busy trying to convince us that a blue sky was really pink.
Here is the word usage from the IEEE standards style manual.
13. Word usage
13.1 Shall, should, may, and can
The word shall is used to indicate mandatory requirements strictly to be followed in order to conform to the standard and from which no deviation is permitted (shall equals is required to).
The use of the word must is deprecated and shall not be used when stating mandatory requirements; must is used only to describe unavoidable situations.
The use of the word will is deprecated and shall not be used when stating mandatory requirements; will is only used in statements of fact.
The word should is used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but not necessarily required; or that (in the negative form) a certain course of action is deprecated but not prohibited (should equals is recommended that).
The word may is used to indicate a course of action permissible within the limits of the standard (may equals is permitted to).
The word can is used for statements of possibility and capability, whether material, physical, or causal (can equals is able to).
