Re: _atom_site_aniso_label is broken

[James Hester <jrh@xxxxxxxxxxxx>]

As the Bearded One is maintaining a Delphic silence, let me summarize
where I think we're at:

I state that a (any?) reading of the DDL1.4 spec implies that
_atom_site_aniso_label is broken.

Nick explains that the parent/child relationship between
_atom_site_aniso_label and _atom_site_label means that they can be used
as keys to join/split loops even during validation, consequently solving
the list_mandatory and _list_reference problem.

Now I pick up the ball again:

This database joining behaviour is obviously desirable, and I'm happy to
go with whatever is standard, but *where* is this described?  Shouldn't
this be mentioned in a standards document somewhere?  Why is the
document describing DDL1.4 completely silent on these implicit joins?  I
attach some relevant paragraphs from the DDL1.4 spec
ftp://ftp.iucr.ac.uk/pub/ddldic.c95 - where would we expect to see an
explanation of this behaviour?

================
data_category
    _definition
;              Character string which identifies the natural grouping of data
               items to which the specified data item belongs. If the data
               item belongs in a looped list then it must be grouped only with
               items from the same category, but there may be more than one
               looped list of the same category provided that each loop has its
               own independent reference item (see _list_reference).
  

data_list_link_child
    _definition
;              Identifies data item(s) by name which must have a value which
               matches that of the defined item. These items are referred to
               as "child" references because they depend on the existence 
               of the defined item.
;
    _name                      '_list_link_child'
    _category                    list_link_child
    _type                        char
    _list                        both


data_list_link_parent
    _definition
;              Identifies a data item by name which must have a value which
               matches that of the defined item, and which must be present in
               the same data block as the defined item. This provides for a 
               reference to the "parent" data item.
;
    _name                      '_list_link_parent'
    _category                    list_link_parent
    _type                        char
    _list                        both

data_list_mandatory    
    _definition
;               Signals if the defined item must be present in the loop 
                structure containing other items of the designated _category. 
                This property is transferrable to another data item which is
                identified by _related_item and has _related_function set as
                'alternate'.

data_list_reference 
    _definition
;              Identifies the data item, or items, which must be present
               (collectively) in a looped list with the defined data item 
               in order that the loop structure is valid. The data item(s)
               identified by _list_reference provides a unique access code 
               to each loop packet. Note that this property may be trans-
               ferred to another item with '_related_function alternate'.
;            
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