[Nexus] Status of NAPI

[Andy Gotz]

Ray,

does this mean the the goal is still to propose NAPI as the official way 
to write Nexus files? Developing and maintaining an API is a lot of 
work. I wonder if a community like Nexus which has very limited 
resources should take on more work. I remember issues in the past with 
multi-threading and bugs which make the NAPI difficult to use. Without 
adequate resources these problems will come back.

Our preference is to use the HDF5 libraries directly even for Python 
(h5py).

Andy

On 21/06/2015 22:23, Osborn, Raymond wrote:
> 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
>>> _______________________________________________
>>> NeXus mailing list
>>> NeXus at nexusformat.org <mailto:NeXus at nexusformat.org>
>>> http://lists.nexusformat.org/mailman/listinfo/nexus
>>
>>
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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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