NIAC Decisions on NeXus Classes

This section records NIAC decisions on NeXus base classes and application definitions.

NIAC 2003: Instrument definitions and base classes will be fully self describing

NIAC 2003: Instrument definitions and base classes to go into CVS

NIAC 2003: analysis item in NXentry to be replaced with definition

NIAC 2003: NXroot will be defined as

<NXroot file_name="{File name of original NeXus file}"
     file_time="{Date and time of file creation}"
     file_update_time="{Date and time of last file change at
     NeXus_version="{Version of NeXus API used in writing the
     creator="{facility or program where file originated}?">
     <NXentry name="{entry name}">+</NXentry>

NIAC 2003: base classes and instrument definitions will not define bit length for primitives. This means that NX_UINT, NX_INT or NX_FLOAT are all that are allowed for numerical items.

NIAC 2003: The template for NXentry is

<NXentry name="{Entry Name}">
     <title>{Extended title for entry}</title>
     <definition version="{DTD version number}" URL="{URL of DTD
        file}">{Name of entry DTD}</definition>
      <start_time type="ISO8601">{Starting time of
     <end_time type="ISO8601">{Ending time of
     <duration type="NX_INT" units="seconds">{Duration of
     <run_number type="NX_INT">{Number of run or scan stored in
        this entry}</run_number>
     <run_cycle type="NX_CHAR[]">{}</run_cycle>
     <program_name version="{Program version number}">{Name of
        program used to generate this file}</program_name>
     <command_line>{Name of command line used to generate this
     <notes>{Notes describing entry}</notes>
     <NXuser name="{user}"></NXuser>
     <NXsample name="{sample}"></NXsample>
     <NXinstrument name="{Name of instrument}"></NXinstrument>
     <NXmonitor name="{Name of monitor}"></NXmonitor>
     <NXdata name="{Name of data block}"></NXdata>

NIAC 2003: NXinstrument template consists of at least the following groups

     <name short_name=”{abbreviated name of instrument}”>{name of instrument}</name> 

NIAC 2003: Each NXlog will contain information for one variable The definition of a NXlog is

<NXlog name=”{identifier for the log}”> 
        <description>{longer description of what is logged}</description>
        <time start=”{written in ISO8601}” units=””  type=”NX_FLOAT”>{time axis for logged quantity}
       <value units=”{units of logged value}”  type=”NX_FLOAT|NX_INT”>{array of logged value, such as temperature}</value> 
       <raw_value units=”{units of raw values}”
            type=”NX_FLOAT|NX_INT”>{array of raw information, such as voltage on a thermocouple}?</raw_value> 

NIAC 2004: NXcharacterisations is removed from NXentry

NIAC 2004: End-of-line in NXnote is cr

NIAC 2005: describe links as NAPIlink in metaDTD

NIAC 2005: Allow ? and * in definitions to denote groups and fields that are desirable but not necessary.

NIAC 2006: TOF Raw definition ratified

NIAC 2006: Add synchrotron changes to NXsource

NIAC 2006: Add NXinsertion_device

NIAC 2006: Add NXbending_magnet

NIAC 2007: NXmonopowder ratified

NIAC 2007: NXpositioner ratified

NIAC 2007: NXmonitor ratified

NIAC 2007: All classes ratified will be NeXus 2.0.

NIAC 2007HMI: ratified NXcone definition (check where this one is)

NIAC 2007HMI: replace run_number with entry_identifier in NXentry

NIAC 2007HMI: ratified NXarchive

NIAC 2007HMI: ratified NXdetector extensions for CCD cameras: 1. extend type to include: ccd,pixel,image_plate, cmos 2. add field data_file 3. add field flood 4. add field flood_file 5. add field dark 6. add file dark_file 7. add field spatial_distortion 8. add field spatial_distortion_file

NIAC 2010: NXcollection ratified

NIAC 2010: tags scalar, image for datasets

NIAC 2010: muon application definition ratified with some changes

NIAC 2012: NXcharacterisation deprecated

NIAC 2012: add some DECTRICS required fields to NXdetector

NIAC 2014: NXmx, NXtransformations and variants ratified

NIAC 2014: Ratified NXarpes, NXCite with addition of URL, NXfresnel_zone_plate

NIAC 2014: Add a default attribute at root and NXentry level to help in finding default data to plot

NIAC 2014: added decimated as a possible enum to acquisition_mode in NXdetector

NIAC 2014: additional field nominal added to NXmonitor to keep the nominal flux

NIAC 2014: “rgbimage”, “rgbaimage”, “hslimage”, “hslaimage”, “cmykimage” to be added to the interpretation attribute of datasets to encode 3d datasets with colour as added dimension to the 2d image.