The rule grammar

Every rule Product Configurator can hold reads:

WHEN an option is a value [AND an option is a value …]
THEN <verb> <target>

Conditions are joined with AND and with nothing else. Two rules with the same target are already an OR, so write two rules where you mean one. Rules are not ordered: nothing about how a product resolves depends on which rule you wrote first.

Verbs

Verb	What it does
hide	The target is taken away while the conditions hold. An option that is hidden stops being required as well, whatever its own flag says, so there is no make optional verb to look for — and an answer already typed into it is kept, disabled, in case the rule stops firing.
show	The target is hidden until one of its show rules fires. Naming a target in a show rule is what makes it hidden by default, which is how the grammar says normally not offered without a second checkbox on another screen.
require	The target must be answered while the conditions hold. It flips OpenCart's own required flag, so the refusal, its wording and the control it appears against are all OpenCart's. It applies only to an option that ends up visible, so a rule that hides an option beats a rule that requires it.

Where two verbs disagree about the same target, hiding wins. That is the only safe direction: the other one would let you build a product nobody can buy.

Targets

Target	What it names
the option (option)	A whole option of the product — the control and every value in it.
the value (value)	One value of one option, leaving the rest of that option alone. This is the compatibility case: pick a motherboard, and the memory sizes it will not take disappear from the list rather than the list disappearing.

require is the one verb with no value form: OpenCart carries a required flag per option and none per value, so there is nothing for it to flip on a single value.

What a condition may be written against

A condition names an option and one of its values, so only the option types whose answers are values you set in advance can hold one. Text, a date, a time and an uploaded file cannot: a condition on those would be matching whatever the customer typed.

Option type
select	A dropdown. One answer, from values you set in advance.
radio	A radio group. One answer, from values you set in advance.
checkbox	A checkbox group. Several answers at once, so is means is among the values ticked.

A target may be an option of any type. It is only the WHEN side that is restricted — so a rule can perfectly well reveal an engraving text box, or require a file upload.