[h5md-user] File format versioning

[pdebuyl]

Hi all,

This is a follow up on the discussion about the file format version number. See
message http://article.gmane.org/gmane.science.simulation.h5md.user/658 and the
discussion that led to it.

The question is: do the following changes require a major version number change?

1. Make 'time' optional in time-dependent elements.
2. Allow 'time' to be Integer.
3. Get rid of 'step' and 'time' altogether so that they are replaced by scalar
   datasets with the proper information for linear spacing.

Reminders:
"""
The version x.y.z of the H5MD specification follows semantic versioning
(Preston-Werner): A change of the major version number x indicates
backwards-incompatible changes to the file structure. A change of the minor
version number y indicates backwards-compatible changes to the file structure.
"""

But semantic versioning is not clear on file formats (to me at least). If the
changes above alow H5MD software written recently to handle 1.0 and 1.1 (for
instance), does it qualify as "backwards-compatible"?

Personally, I don't care for the result. What is important is that we may find a
suitable solution. Also, given H5MD's recent character, I consider it possible
to make such changes. The number of software using H5MD is still small and the
improvements discussed recently might prove important to get a wider use.

P

PS: in my recent use, I am starting to be annoyed about the lack of
connectivity. This is just a PS because it belong in another thread.