A BOSS business object can be related to one or more collections of composed child objects. For example, an Order object can compose a related collection of OrderLine child business objects. A parent object, like Order, can have multiple composed child collections, and each collection can comprise business objects that, in turn, contain composed collections. For example, each OrderLine business object that is part of an Order can have a composed collection of OrderLineFulfillment child business objects.

When working with a root business object like Order that has a composed child collection, clients like APEX can read and write child objects using a nested resource name that includes the resource key of a specific parent object. For example, to list the OrderLine child objects for order 12345, the REST endpoint would end with the path:

/orders/12345/orderLines

In the previous example, 12345 is the resource key of a specific order, and orderLines is the name of the Order object’s accessor attribute of type object-collection.

To work with the child objects of a specific OrderLine with resource key 67890, on a specific Order with resource key 12345, the REST endpoint URL would end with:

/orders/12345/orderLines/67890/orderLineFulfillments

The orderLineFulfillments is the name of the OrderLine object’s accessor attribute of type object-collection.

You can define REST Data Sources for the nested resources, using a named parameter in the URL path like this for the order lines:

/orders/:orderId/orderLines

To access a second-level child, the REST Data Source’s endpoint URL can contain multiple URL path parameters, for example:

/orders/:orderId/orderLines/:orderLineId/orderLineFulfillments

When using these parameterized REST Data Sources in a region on a page, you can then bind the value of the REST Data Source’s URL path parameters under the Parameters node in the Rendering tab for the region to use an appropriate page item.