[NeXus-committee] NeXus XML format and reduced data files

[Akeroyd, FA (Freddie)]

The Small Angle Scattering (SAS) community have been working on a
reduced data file format and I enclose an example (tk49.xml) of what
they seem to be converging on. You'll notice that the file looks very
simililar to a NeXus XML file, but there is an important difference on
how the numerical Q, intensity, and error data is stored. 

The current NeXus XML interface stores all the values of an array
together under one XML tag - this makes it harder to read the data into
other programs that extract logical columns of numbers. The enclosed
tk49.xml satisfied this by having the numbers in fixed format column
locations, but also surrounded by XML tags that allow easy extraction
into named Excel columns (see http://www.ill.fr/lss/canSAS/XML_SAS.htm).
Note that this webpage shows Excel 2003 - the latest Excel 2007
automatically recognises the file structure and puts up a Task Pane from
which the user can browse for the data or metadata they want.

data_comparisons.xml compares the current NeXus XML format with a
proposal for an alternative XML representation based on the ideas above.
I have had a look at the NeXus XML source code and, with some work, it
should be possible to support both this and the current XML format. I
believe it would be advantageous to NeXus if the SAS community were to
use the NeXus API with their reduced data files - they will also gain by
getting access to NeXus (and HDF) tools to manipulate their reduced
data.

What do people think about the API supporting a second XML format? The
SAS community will be discussing data formats at the upcoming canSAS-V
meeting (http://www.smallangles.net/canSAS/schedule.html) - if we wish
to collaborate on a second XML representation that meets their specific
needs while maintaining generality we will need to decide soon.

Freddie
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