Records contain for each bound state the term energy and configuration assignment.
Indexing on the energy entity e is organized such that a hierarchy of access is enforced. This design consideration was adopted bearing in mind the types of queries most likely to be performed by users. For instance, when the nuclear charge nz is kept constant and ne is given a range, the query type is referred to as isonuclear . Similarly, if the number of electrons is assigned a fixed value and the nuclear charge is given a range, the query is said to be of the isoelectronic type. If nz and ne are given constant values, the query will address data belonging to an ion, and therefore may be called an ionic query.