OCL groupBy expression groups together a collection of all matching objects based on a specified criterion, returning a tuple of the grouping criteria object and a collection of the matching objects in the List property.

groupBy is well-suited for aggregation with its ability to utilize tuples, enabling the creation of aggregate expressions for extraction of patterns from model-driven data that can be used for statistical analysis.

Example

To get the product sales made on specific dates:

NOTE: The groupBy expression always returns the grouping criteria object and a collection of matching objects grouped based on the criteria.

To get product sales made on specific dates with the quantity and sales amount:

Tuples can be used to create more aggregations from our data, which can then be accessed as parts of the tuple.

Tuple Parts (How to access the data)	Description
Part1	The grouping criteria object accessed with grouping object name .DateAdded instead of .Part1 since it is known and available in the groupBy result.
Part2	The total quantity sold accessed as .Part2 since it is computed and not available in the groupBy result.
Part3	The total sales amount accessed as .Part3 since it is also computed and not available in the groupBy result.