Re: [h5md-user] Multiple H5MD root groups per file

[Peter Colberg]

On Fri, Sep 20, 2013 at 01:14:59PM +0200, Konrad Hinsen wrote:
> Pierre de Buyl writes:
> 
>  > I propose one of these updates:
>  > 1. Mandate a list of H5MD paths somewhere at the root of the file (for
>  > autodiscovery of H5MD containers).
> 
> If we want to be able to use H5MD inside a collection of data managed
> by some other specification, then we cannot mandate anything to be at
> the root level. Any prescription about the root level more or less
> implies "we own the whole file".
> 
> It's actually not so difficult to let programs search for H5MD data
> inside a file. The real difficulty is what to do when there are
> multiple H5MD trajectories but the operation of the program requires a
> single one.
> 
>  > 2. Allow the extension but mandate that H5MD data be communicated as
>  > file.h5/path/to/some/h5md_root_group.
> 
> No problem with that but it's a bit outside of the specification of the
> file format.
> 
> BTW, I'd use some other separator between filename and path, otherwise
> it's difficult for Unix software to identify the filename. Of course anything
> else could conflict with some other platform's path separator.

I don't think we need or should worry about communicating the path(s)
to H5MD roots. An H5MD root is intended to be a self-contained unit,
so by definition it cannot point to itself from outside the H5MD root.

Finding the H5MD roots in a file is a task to be solved by the program.
Simple programs can ask for a path+group instead of a just a path, and
more complex programs can locate root(s) by walking the HDF5 file.

Peter