Re: [h5md-user] Metadata on physical quantities and their units

[Peter Colberg]

Hi Pierre,

On Fri, Aug 02, 2013 at 03:47:53PM -0400, Pierre de Buyl wrote:
> One possibility, with H5MD, is the ability to have subgroups. Imagine
> combining two molecular structures that come from separate sources.
> With a global unit settings for units, as opposed to a named datatype,
> this would be error-prone.

That is a good example, I had not thought of that.

The solution to this problem lies along the same line as with the
"parameters" group. When merging from two different sources with
conflicting parameters groups, one could use subgroups such as
"/parameters/source1" and "/parameters/source2". The physical units
could be merged using subgroups "/h5md/quantities/source1" and
"/h5md/quantities/source2".

The nice thing about using data types for the units is that their
location within the "quantities" group does not matter. A data type
can be moved around in the file, like other objects, and the data
using the data type will always point to the correct location.

> Given the lack of actual use, as of now and in the context of H5MD,
> could we not wait?

Yes, that is what I suggested earlier. I am bringing up a complete
proposal to provoke thoughts on a solution, and it did indeed ;-).

Peter