Require Template
The Require template has the form:
[item or condition] requires [item or condition]
A require constraint is a logical implies. If the first operand is true then the second operand is implied (must be true). For example, Item A requires Item B. This constraint means that if Item A is present in the solution, then Item B must be present. Another example: Condition A requires Item B. This constraint means that if Condition A is true, then Item B must be present in the solution.
A require constraint is not mutual. The constraint Item A requires Item B does not imply Item B requires Item A. However, if Item B is excluded then Item A is also excluded. This is because when Item B is excluded, the constraint can never be true.
The require operator is functionally equivalent to the following Boolean expression:
(NOT A) OR B
In the first two columns of the following table, a 1 means the item is present in the solution. A 0 means it is absent or excluded.
| A | B | NOT A | (NOT A) OR B |
|---|---|---|---|
1 |
0 |
0 |
False |
0 |
1 |
1 |
True |
0 |
0 |
1 |
True |
1 |
1 |
0 |
True |
The table shows that a require constraint behaves as follows:
False when Item A is present and Item B is not. (If Item B cannot be present, Item A cannot be present).
True when Item B is present and Item A is not.
True when neither is present.
True when both are present.
Use require constraints to:
To create a requires relationship for items in different relationships. For example, you can write a constraint that if Item A in relationship 1 is picked, then Item B in relationship 2 is required.
To add items to the configuration if a condition is true.
To create relationships between other items (conditions) when a product is added to the solution.