[NeXus-committee] DECTRIS example summary

[Watts Benjamin]

I think that everyone is looking at the Dectris data the wrong way. It
is a single data array and is only broken up into separate files because
of performance issues. Therefore, ideally, all the data shoud be written
into a single NXdata group. Since we are forced to receive it in
separate files, linking is an obvious solution. However, links in NeXus
have always been discrete - mapping one location to one array in another
location. Our situation here is different, with the one array being
separated into a number of pieces in different locations. The master
file needs some way of saying "my data is there, and then continues
there, and there and there...", which does not yet exist (to the best of
my knowledge). Options for doing this include:

1. The NXdata group of the master file contains a list of external
links, with the order of the list describing the order in which the
linked arrays should be concatenated.
2. The master NXdata group links to the first part of the array and then
the file containing that first part has some record pointing to where
the data is continued.
3. Both could be done together.

Option #1 seems best to me.

Cheers,
Ben

-----Original Message-----
From: nexus-committee-bounces at nexusformat.org
[mailto:nexus-committee-bounces at nexusformat.org] On Behalf Of yayahjb
Sent: Montag, 14. Januar 2013 15:18
To: Koennecke Mark
Cc: fcb at bernstein-plus-sons.com; Discussions of the NeXus Advisory
Committee
Subject: Re: [NeXus-committee] DECTRIS example summary

The one fussy disagreement I have with this summary would be on
signal=1.  I am not sure this matters, but I think the current rule is
that we are only supposed to have one dataset with "plottable" data,
i.e.
with signal=1.  If that rule is important, then I we probably should ask
for signal=2, signal=3, etc. on the second, third, etc. dataset.
I think this is actually consistent with an old NeXus rule when you had
multiple datasets.  The alternatives would be to change the rule and say
either:

   You can have multiple plotable datasets with signal=1 or

   The plotable datasets have signal=n, where n designates the order of
plotting, starting with 1.

The second version would be consistent with this particular data.

Sorry to be fussy

   Regards,
     Herbert


On 1/14/13 8:38 AM, Mark Koennecke wrote:
> Hi,
>
> from your feedback and my own study I find that there are the 
> following problems with the example file as is:
>
> - Structure is wrong regarding linked data sets. Should be either:
>
>   * entry:NXentry/data_00001:NXdata/data (Preferred ....)
>   * entry:NXData/data:NXdata/data_0001
>
> - On data, signal=1 attribute is missing
> - On external link, NeXus attribute
> NAPIMOUNT=nxfile://th02c_ps02_1_data_000001.h5#data
>   missing
> - In detector, flatfield, efficiency data is missing. This is not 
> critical,
>   I just wonder.
>
> Am I right? Is this what I tell DECTRIS tomorrow? Or do I miss
something?
>
> Also, what is the opinion, do we need another Telco on this one?
>
> Regards,
>
>              Mark
>
>
> _______________________________________________
> NeXus-committee mailing list
> NeXus-committee at nexusformat.org
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>

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