Section 2.5.5.6. Definition example 6: mandatory and linked items

The example definition in Fig. 2.5.5.6 shows the attributes for the item _atom_site_label. As illustrated in Section 2.5.5.5, this item is the reference key to a list of items belonging to the category ATOM_SITE. The attribute _list_mandatory, which is set to a value of yes, specifies that this item is a mandatory item to a list of category ATOM_SITE items. The attribute _list_link_child identifies items in other categories that are `linked' by derivation to this item and therefore share the same data values. This dependency is known as a child dependency. The definition shows that data items describing the labels of atom sites in a list of angular geometry, i.e. _geom_angle_atom_site_label_1 and _geom_angle_atom_site_label_2, are the same labels described by _atom_site_label in the atom-site list. This is because the geometry is derived directly from the atom-site data. Note that this dependency requires that the ATOM_SITE list be present in the same CIF as the GEOM_ANGLE list, otherwise the molecular geometry information cannot be linked to the three-dimensional structural information.

Figure 2.5.5.6 | top | pdf | DDL1 definition of a `mandatory' data item.