Single-Level "Hierarchies"
Some types of information may not be hierarchical by nature. In this case, you can still define a "hierarchy," but it can consist of a single level. In searches, single-level hierarchies function as a list of values.
Some types of information may not be hierarchical by nature. In this case, you can still define a "hierarchy," but it can consist of a single level. In searches, single-level hierarchies function as a list of values.