You can use product in an OCL expression when you need every pairing between the objects in one collection and the objects in another collection.
Syntax
product ( c2 : Collection(T2) ) : Set(Tuple(first : T, second : T2))
What product returns
product returns a Set of Tuple values representing the Cartesian product of the collection before product and c2.
A Cartesian product contains one tuple for every possible pair:
firstis an element from the collection beforeproduct.secondis an element fromc2.
The result is a Set, so the result contains tuple values rather than an ordered sequence.
Example
If the first collection contains 1 and 2, and the second collection contains 'A' and 'B', the expression below creates all four possible pairs.
Set{1, 2}.product(Set{'A', 'B'})
The result is a set equivalent to:
Set{
Tuple{first = 1, second = 'A'},
Tuple{first = 1, second = 'B'},
Tuple{first = 2, second = 'A'},
Tuple{first = 2, second = 'B'}
}
Use product when the rule or query needs to consider every combination of two collections. For example, a model can use the returned tuples as the input to a further OCL expression that evaluates each pair.
Empty collections
If either collection has no elements, there are no pairs to create. The Cartesian product is therefore an empty set.
Related OCL operators
product is a collection operation. For the wider operator set and guidance on finding available operators in the OCL editor, see Documentation:OCLOperators and Documentation:OCL General Operators. OCL expressions are declarative and must not have side effects; see Documentation:OCL Expressions.