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International
Tables for Crystallography Volume G Definition and exchange of crystallographic data Edited by S. R. Hall and B. McMahon © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. G. ch. 2.5, p. 56
Section 2.5.5.7. Definition example 7: joinable lists
a
School of Biomedical and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia, and bBCI Ltd, 46 Uppergate Road, Stannington, Sheffield S6 6BX, England |
In the example definition shown in Fig. 2.5.5.7![[link]](/graphics/greenarr.gif)
, the key item _atom_site_aniso_label is shown to have a special relationship with the key item _atom_site_label. This is because the data items in the list category ATOM_SITE_ANISO may be merged with (i.e. joined to) items in the list category ATOM_SITE. If this happens, the item _atom_site_label assumes the role as the key to the merged packets and this is signalled using the attribute _list_link_parent. When these two categories appear in separate lists, the category ATOM_SITE_ANISO data require the category ATOM_SITE data to be present in the data instantiation, but not vice versa. Note that the parent relationship, unlike that in the example of Section 2.5.5.6 arising from a derivation dependency, is because ATOM_SITE_ANISO is a subcategory of ATOM_SITE.
![[Figure 2.5.5.7]](/figures/Gafig2o5o5o7thm.gif)
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DDL1 definition of a `parent' data item. |
