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<div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Helvetica,sans-serif;" dir="ltr">
<p>Hi Tobias,</p>
<p> I agree that we have spent the past decade recommending HDF5, but at the same time we have been saying that NeXus is about the organisation of data within the container, not the container file format itself. I can see that you feel surprised by the sudden
discussion of other file formats, just as I was surprised to hear the community talking about it at the recent NFDI workshop. I am only advocating for discussion and I would like to hear your input.
<span>I agree that multiple backends will introduce higher support requirements that NeXus doesn't currently have resources for.</span> Your preference for NeXus referring to a (small) defined set of file formats is a valid view point and I agree that there
are practicalities to consider. I view the next telco as just the restart of an old discussion and nothing can really change until a proposal is brought to a NIAC meeting (and accepted).</p>
<p><br>
</p>
<p>Cheers,</p>
<p>Ben<br>
</p>
</div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Tobias Richter <Tobias.Richter@ess.eu><br>
<b>Sent:</b> Thursday, 7 April 2022 6:23:43 PM<br>
<b>To:</b> Discussion forum for the NeXus data format; nexus@nexusformat.org<br>
<b>Cc:</b> Watts Benjamin (PSI); Alexander Debus; Nicolas Soler; Franz Pöschel; Emilio Centeno Ortiz<br>
<b>Subject:</b> Re: [Nexus] HDF5 as NeXus file format</font>
<div> </div>
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<div class="WordSection1">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">According to this discussion from a decade ago HDF5 is singled out as the only preferred physical file format:
<a href="https://www.nexusformat.org/NIAC2012">https://www.nexusformat.org/NIAC2012</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<ul type="disc">
<li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">NeXus guiding statements:<o:p></o:p></span>
<ul type="circle">
<li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">The main focus of the NeXus community is to further develop the dictionaries, base classes and application definitions.<o:p></o:p></span></li><li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">The NIAC is a forum for resolving issues.<o:p></o:p></span></li><li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">The NIAC acts as a custodian for NeXus: definitions, examples, documentation, reference implementations.<o:p></o:p></span></li><li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">NeXus can be mapped to different physical file formats:<o:p></o:p></span>
<ul type="square">
<li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level3 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">HDF5 is the preferred physical file format.<o:p></o:p></span></li><li class="MsoNormal" style="color:#515151;mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level3 lfo1;background:white">
<span style="font-size:13.5pt;font-family:"PT Sans",sans-serif">NeXus-XML is the currently supported ASCII file format.<o:p></o:p></span></li></ul>
</li></ul>
</li></ul>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Technically you can map into different backends. Yes. XML is still sort of supported. At the time it was requested that other options would get the official blessing (YAML being specifically asked
for) but for practical exchange between facilities the consensus was to stick with HDF5.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">There no longer is a recommended or fully maintained abstraction layer (like NAPI) to do an on the fly translation between backends. Who would be in charge of defining how the “official” mapping
into sqlite or whatever would look like? How many backends can the community commit to support in the long run?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">When tools that are currently developed/supported/maintained to “read” NeXus/HDF5 fail to work with what gets handed out, we are in a worse situation than we are now. Note: What facilities do internally
for performance optimisations or other reasons could be different, if it stays internal. But I am clearly a lot less open minded about producing non-HDF5 files with a “NeXus” label than Ben. Maybe I missed some decisions that were taken lately in this direction
or we’re no longer interested in being able to read each other’s files. Should either be the case, I’ll be quiet.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Best wishes,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Tobias<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-left:36.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">NeXus <nexus-bounces@shadow.nd.rl.ac.uk> on behalf of "Watts Benjamin (PSI) via NeXus" <nexus@shadow.nd.rl.ac.uk><br>
<b>Reply to: </b>Discussion forum for the NeXus data format <nexus@shadow.nd.rl.ac.uk><br>
<b>Date: </b>Thursday, 7 April 2022 at 17:10<br>
<b>To: </b>"nexus@nexusformat.org" <nexus@nexusformat.org><br>
<b>Cc: </b>Benjamin Watts <benjamin.watts@psi.ch>, Alexander Debus <a.debus@hzdr.de>, Nicolas Soler <nsoler@cells.es>, Franz Pöschel <f.poeschel@hzdr.de>, Emilio Centeno Ortiz <ecenteno@cells.es><br>
<b>Subject: </b>Re: [Nexus] HDF5 as NeXus file format<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:36.0pt"><o:p> </o:p></p>
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<div id="divtagdefaultwrapper">
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Hi Gabriel,<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black"> NeXus is officially not dependent on HDF5 and we are definitely open minded about implementing the NeXus
<i>data format</i> on <i>file formats</i> other than HDF5. We plan to discuss such issues at our
<a href="https://www.nexusformat.org/Telco_20220426.html">next teleconference</a> on April 26th and I invite you to join us. Are there specific container file formats that you are interested in?<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Cheers,<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Ben<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:36.0pt">
<span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<div>
<div class="MsoNormal" align="center" style="margin-left:36.0pt;text-align:center">
<span style="font-size:12.0pt;color:black">
<hr size="0" width="100%" align="center">
</span></div>
<div id="divRplyFwdMsg">
<p class="MsoNormal" style="margin-left:36.0pt"><b><span style="color:black">From:</span></b><span style="color:black"> NeXus <nexus-bounces@shadow.nd.rl.ac.uk> on behalf of Gabriel Jover Manas via NeXus <nexus@shadow.nd.rl.ac.uk><br>
<b>Sent:</b> Thursday, 7 April 2022 4:47 PM<br>
<b>To:</b> nexus@nexusformat.org<br>
<b>Cc:</b> Gabriel Jover Manas; Nicolas Soler; Emilio Centeno Ortiz<br>
<b>Subject:</b> [Nexus] HDF5 as NeXus file format</span><span style="font-size:12.0pt;color:black">
<o:p></o:p></span></p>
<div>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Dear NeXus Users Community,
<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Last NFDI NeXus Workshop was a great opportunity to meet the community and learn from the experience of other scientists and institutions.<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Here at ALBA we are working on the integration of NeXus files in our data analysis workflows.<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">In this scope we are interested on investigating alternatives to hdf5 as NeXus file format, in terms of slice read/write performance, read-write-many capabilities and convenient reading.<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Would the community be open to decoupling the data format (NeXus) from the file format (HDF5)?<br>
Is there already any effort in the community in this direction?<br>
Is anyone else also interested?<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Best regards,<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Gabriel<o:p></o:p></span></p>
<p style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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