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Using the structural metadata for tree navigation one can fetch the (direct) children of a record or get the grandparents of a record.

Reference Codes & Has (Non Representation) Children

The metadata field Structural.ReferenceCodes is an ordered multi-item field (see Complex Fields) containing the record IDs from the parents, starting from the oldest / first.

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Once a record obtains its first child the field HasChildren will be set to true for the parent. Even if the child is later on permanently deleted, the field HasChildren will be true forever on the parent.
Data objects, e.g., the record type Media, always have HasChildren set to true because it has direct (grand)children representations. In order to know whether the data object has other data objects that are children, e.g. emails with attachments, a new field HasNonRepresentationChildren has been introduced in version 23.4.

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