You can dynamically add children to an instance list on demand

You can dynamically add children to an instance list "on demand"

In this example you could just add the three SECTIONS like this:

When the user goes to expand the section ADM-01 (say) in the visual tree a check is made to see if you have specified a Relationship Handler for the relationship between SECTIONS and EMPLOYEES.

If you have, then it is called to "expand" the relationship between SECTION ADM-01 and the EMPLOYEES that work in the section. After it has been called, the physical instance list would look like this:

At the end of this section is an example of a RDML function used to handle the expansion if the relationship between SECTIONS and an EMPLOYEES.  

If you create a relationship handler to dynamically expand entries in an instance list then you need to identify it to the Framework on the Instance List / Relations tab as the Relationship Handler here: