Fwd: Re: DDLm, dREL, images and NeXus

[Doug]

On Fri, 12 Dec 2008, Herbert J. Bernstein wrote:
> I'll say more later, when other have had their say, but Doug's
> suggestion of simply mapping the data needs a prompt response:
> especially when working with 3D data, or even when working
> witn 2D data in a 3D lab coordinate frame, it is very hard,
> and perhaps infeasible, to specify the complete mapping without
> the ability to specify methods, e.g. when working with multiple
> coordinate frames or different handedness.  Life is mich simpler
> when you can specify the algorithm for going from one to another.
> A more subtle need for algorithms is in specifying the mappings
> between a failry well normalized database dump (e.g. imgCIF)
> and a rather denormalized format (e.g. NeXus).


I am wondering if there is a possibility to aim a bit lower?

James' example basically just says  audit_author.name = NXuser.name
- that its in a looped/multiple-instance context is reasonably obvious
(Mind you, if there is a single author in NeXus, does that necessarily
have to convert to a CIF loop_ ?).

What is the most complicated transform you are expecting?
Isn't it likley that most items will be one-to-one mappings, 
a few might be simple linear transforms and anything more
complicated would be outsourced to dedicated routines/code anyway 
(certainly on the metadata side of things, I would guess)? 

As a fall back, maybe the existing dictionaries could be enhanced with
CIF definitions that hold interim items that need further work done on them
(I'm assuming NXdata can hold anything whatsoever without definition on the NeXus side).

Do you really need a complete algorithm language and dedicated parser?

Doug




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