Re: [h5md-user] Specifying the data type

[Pierre de Buyl]

Hi,

On Thu, Aug 29, 2013 at 10:23:19AM +0200, Felix Höfling wrote:
> Am 29.08.2013, 09:49 Uhr, schrieb Olaf Lenz <address@hidden>:
> 
> >Hi!
> >
> >I want to propose to extend the notation of the H5MD trees and subtrees
> >to include the datatype. Example:
> >
> >    <data_group>
> >     \-- step: INT[variable]
> >     \-- time: FLOAT[variable]
> >     \-- value: <type>[variable][...]
> >
> >This makes it easier to get what is meant from the specification, and I
> >do not think it clobbers the output overmuch.
>
> Capitalised identifiers remind me of Fortran ... how ugly, but HDF5 uses
> them as well :-(
> 
> More seriously, there is not just one integer or float type in HDF5. For
> this reason, the H5MD spec just states "of integer data type" or
> "real-valued". And for the most interesting datasets, the actual data in
> "value", the data type is unspecified at all as it depends on the specific
> data stored.
> 
> I feel that expressing all that by the tree graphs would overload them,
> the focus should be on the tree structure. And for the details, the user
> is encouraged to read the text, not just to look at the pictures ;-)

Actually, the only datatype that is really important is the integer datatype for
"step" and for some data such as "id". HDF5 is otherwise flexible and I would
avoid (i) clobbering the specification and (ii) putting constraints where it is
not needed.

Best,

Pierre