[Nexus] Status of NAPI

[Osborn, Raymond]

I had understood that there were plans to create a light version of the NAPI, which was only dependent on HDF5. I am slightly concerned about encouraging people only to use HDF5 directly, because that makes it entirely dependent on them to ensure compliance with the NeXus rules - e.g., by adding a group attribute, NX_class, to each group.

Ironically, NAPI was written to remove much of the complexity in writing files by having a reduced set of functions. HDF5 is better written than HDF4 in this respect, but the additional flexibility still makes it quite daunting to learn. The NeXus API is a model of simplicity so a lightweight API would still make sense.

Ray
P.S. Of course, I would encourage people to use the Python interface (http://nexpy.github.io/nexpy/), which is even simpler, and ensures compliant NXdata groups as well.

On Jun 21, 2015, at 1:04 PM, Tobias Richter <Tobias.Richter at esss.se<mailto:Tobias.Richter at esss.se>> wrote:

Hi Andy,

The official policy just reflects the (perceived) requirements of the community. Your thoughts are correct NAPI is not recommended for new applications. And yes, the manual hasn’t been updated in all areas to reflect this. Please point us to the relevant sections you find unclear. Someone reading the texts with fresh eyes can really make a difference.

Since we focus on HDF5 now, the NAPI backend abstraction (supporting XML and HDF4 in addition) isn’t needed for that. NAPI also provides nothing that would ensure files follow the standard and very little that would at least make conforming easier. So the only benefit is some slight simplification of the hdf5 interface, which denies some of the power of the underlying container format.

That being said, NAPI is not disappearing any time soon, while people rely on it. We should drop support for unused bindings though.

In my view in the long run, some reference application or tools would still be needed to be able to demonstrate interoperability.

Regards,

Tobias


On 21 Jun 2015, at 17:39, Andy Gotz <andy.gotz at esrf.fr<mailto:andy.gotz at esrf.fr>> wrote:

Hi Eugen + Nexus community.

I have a naive question : what is the status of the NAPI? I thought it is being maintained only for legacy applications and that it is not recommended for new applications. But this is not clear from the manual. In some places the reader gets the impression the NAPI is the official API for accessing files conforming to Nexus. In other places the opposite is stated and the hdf5 API is considered as the right way to access files.

What is the official policy on the NAPI?

Andy
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--
Ray Osborn, Senior Scientist
Materials Science Division
Argonne National Laboratory
Argonne, IL 60439, USA
Phone: +1 (630) 252-9011
Email: ROsborn at anl.gov<mailto:ROsborn at anl.gov>


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