A Record in NiFi is made up of (potentially) many fields, and each of these fields could actually be itself a Record. This means that a Record can be thought of as having a hierarchical, or nested, structure. We talk about an "inner Record" as being the child of the "outer Record." The child of an inner Record, then, is a descendant of the outer-most Record. Similarly, we can refer to an outer Record as being an ancestor of an inner Record.