Use "IF" when you mean (or WHEN to use "if")

[John Gear <catalyst -at- PACIFIER -dot- COM>]

someone asked

>"If a truck is in READY status, it is available for assignment."
>"When a truck is in READY status, it is available for assignment."

>convey different meanings.  Or, do they?

>I could use some help.  (How about, "If and when a truck is ... " Just
>joking.)

I follow (and teach) this convention for IF and WHEN statements:

Use IF to introduce a conditional phrase when you want the reader to proceed
(skip to the next step) if the condition is not true.

Use WHEN to introduce a conditional phrase when you do not want the reader
to proceed until the condition is satisfied and they take the action in the
step.

Thus

IF the waste is ignitable OR corrosive,

        THEN mark the barrels with the appropriate chemical hazard symbols.

(If the waste is neither ignitable or corrosive the reader skips the action
and goes on to the next step.  But ...)

WHEN waste has accumulated in a satellite accumulation site for 90 days,

        THEN, before the end of the day, transfer the waste to the TSD unit.

(The reader doesn't skip a conditional statement introduced by WHEN--the
process stops until the WHEN condition is satisfied.)

This seems to work pretty well.  Hope this helps.
John Gear (catalyst -at- pacifier -dot- com)

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