The collection property data type is defined to store multiple object instances of the same type as a property of a parent object, transaction, or fetch. The object type used in a collection property must have a defined key property to uniquely identify each object instance within the collection property. The default initialization for a collection property is an empty collection.
Each object instance within a collection is considered a child instance to the parent definition of the collection property. In objects, collection properties are commonly used to store object instances within a module to provide a data structure within the module representing the relationship between the different business entities for the module. Collection properties defined in the module main object are commonly referred to as “top-level collections”. Collection properties defined within an object other than the main object are referred to as nested collections.
The collection property type may also store other data types. However, in practice there is limited use for this type of definition. A collection defined to store another collection is not valid.