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Re: _atom_site_aniso_label is broken

On Fri, 17 Jun 2005, James Hester wrote:

> In my ideal world, you could work straight off the published specs for 
> DDL1.4 to interpret the cif_core dictionary - am I asking too much?. 
> There is *absolutely nothing* in the _list_link_child and 
> _list_link_parent DDL1.4 entries to indicate any semantics other than 
> that the child can only take values that the parent takes (although you 
> did suggest how this could be enhanced, in, what, 1993?).  And 
> _atom_site_aniso does not exist as a category in cif_core 2.3.

Even in what you say above there must be "implied" semantics (or 
pragmatics). To require the keys must have the same values is meaningless 
without the implication you can do a JOIN. Almost all of the operational 
aspects of DDL1.4 was implied - you will recall at the time the term in 
response to specific questions was universally "that would be application 
dependent". STAR/CIF/DDL1.4 were essentially container framework detailing 
a syntax and a loose structure. What you did with its content was up to 
you given a you included a limited set of "implied" semantics for the DDL.


> So, to present Brian with his choices as I see them...
>
> (1) a transparent fix in the spirit of DDL1.4 which makes current
> behaviour valid (use _list_reference instead of _list_mandatory)

I don't recall the details of DDL1.4 so the meaning of _list_reference is 
hidden in the depths of (my failing) memory. I wouldn't be surprised if 
your perceived fix had some other side-effect.

> (2) a perhaps more controversial fix: create an _atom_site_aniso
> category - this breaks previous cifs where everything was looped
> together, but they are technically broken already.

No it wouldn't break them. The semantics of this structure in StarDDL is 
that you can execute a JOIN on split loops in different (parent-child) 
categories or it can be stored in that form (think of it as a pre-JOIN, 
with you being able to execute a SPLIT, if you so wanted).

> (3) a single line fix: use _related_function 'alternate' - not sure if
> this is really in the spirit of DDL1.

Not sure what this would do either.

Brian is the expert on the DDL1.4 meanings - enlighten us oh bearded one.

> What have other validating CIF programmers done in this case??

<tongue in="cheek">

Which other CIF programmers?

</tongue>

cheers

Nick

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