.. auto-generated by dev_tools.docs.nxdl from the NXDL source base_classes/NXroot.nxdl.xml -- DO NOT EDIT

.. index::
    ! NXroot (base class)
    ! root (base class)
    see: root (base class); NXroot

.. _NXroot:

======
NXroot
======

..
    Contributors List

    .. |contrib_name| replace:: Pete R Jemian|prjemian|https://avatars.githubusercontent.com/u/2279984?v=4|2022-06-13

    .. |contrib_name| replace:: Peter Chang|PeterC-DLS|https://avatars.githubusercontent.com/u/1381719?v=4|2020-10-20

    .. |contrib_name| replace:: Tobias Richter|zjttoefs|https://avatars.githubusercontent.com/u/856440?v=4|2018-05-15

    .. |contrib_name| replace:: Ray Osborn|rayosborn|https://avatars.githubusercontent.com/u/1193959?v=4|2016-04-26

    .. |contrib_name| replace:: Pete R Jemian|prjemian|https://avatars.githubusercontent.com/u/2279984?v=4|2016-04-26

    .. |contrib_name| replace:: Joachim Wuttke (l)|jwuttke|https://avatars.githubusercontent.com/u/5262000?v=4|2014-08-26

**Status**:

  base class, extends :ref:`NXobject`

**Description**:

  Definition of the root NeXus group.

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXentry`

.. index:: NXentry (base class); used in base class

**Structure**:

  .. _/NXroot@NX_class-attribute:

  .. index:: NX_class (file attribute)

  **@NX_class**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: The root of any NeXus data file is an ``NXroot`` class ...

        The root of any NeXus data file is an ``NXroot`` class
        (no other choice is allowed for a valid NeXus data file).
        This attribute cements that definition.

        Obligatory value: ``NXroot``

  .. _/NXroot@file_time-attribute:

  .. index:: file_time (file attribute)

  **@file_time**: (optional) :ref:`NX_DATE_TIME <NX_DATE_TIME>` 

    Date and time file was originally created

  .. _/NXroot@file_name-attribute:

  .. index:: file_name (file attribute)

  **@file_name**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    File name of original NeXus file

  .. _/NXroot@file_update_time-attribute:

  .. index:: file_update_time (file attribute)

  **@file_update_time**: (optional) :ref:`NX_DATE_TIME <NX_DATE_TIME>` 

    Date and time of last file change at close

  .. _/NXroot@NeXus_version-attribute:

  .. index:: NeXus_version (file attribute)

  **@NeXus_version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Version of NeXus API used in writing the file. ...

        Version of NeXus API used in writing the file.

        Only used when the NAPI has written the file.
        Note that this is different from the version of the
        base class or application definition version number.

  .. _/NXroot@HDF_version-attribute:

  .. index:: HDF_version (file attribute)

  **@HDF_version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Version of HDF (version 4) library used in writing the file

  .. _/NXroot@HDF5_Version-attribute:

  .. index:: HDF5_Version (file attribute)

  **@HDF5_Version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Version of HDF5 library used in writing the file. ...

        Version of HDF5 library used in writing the file.

        Note this attribute is spelled with uppercase "V",
        different than other version attributes.

  .. _/NXroot@XML_version-attribute:

  .. index:: XML_version (file attribute)

  **@XML_version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Version of XML support library used in writing the XML file

  .. _/NXroot@h5py_version-attribute:

  .. index:: h5py_version (file attribute)

  **@h5py_version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Version of h5py Python package used in writing the file

  .. _/NXroot@creator-attribute:

  .. index:: creator (file attribute)

  **@creator**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    facility or program where file originated

  .. _/NXroot@creator_version-attribute:

  .. index:: creator_version (file attribute)

  **@creator_version**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Version of facility or program used in writing the file

  .. _/NXroot@default-attribute:

  .. index:: default (file attribute)

  **@default**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Declares which :ref:`NXentry` group contains ...

        .. index:: find the default plottable data
        .. index:: plotting
        .. index:: default attribute value

        Declares which :ref:`NXentry` group contains
        the data to be shown by default.
        It is used to resolve ambiguity when
        more than one :ref:`NXentry` group exists.
        The value :ref:`names <validItemName>` the default :ref:`NXentry` group.  The
        value must be the name of a child of the current group. The child must be a
        NeXus group or a link to a NeXus group.

        It is recommended (as of NIAC2014) to use this attribute
        to help define the path to the default dataset to be plotted.
        See https://www.nexusformat.org/2014_How_to_find_default_data.html
        for a summary of the discussion.

  .. _/NXroot/ENTRY-group:

  **ENTRY**: (optional) :ref:`NXentry` 

    entries


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXroot/ENTRY-group </NXroot/ENTRY-group>`
* :ref:`/NXroot@creator-attribute </NXroot@creator-attribute>`
* :ref:`/NXroot@creator_version-attribute </NXroot@creator_version-attribute>`
* :ref:`/NXroot@default-attribute </NXroot@default-attribute>`
* :ref:`/NXroot@file_name-attribute </NXroot@file_name-attribute>`
* :ref:`/NXroot@file_time-attribute </NXroot@file_time-attribute>`
* :ref:`/NXroot@file_update_time-attribute </NXroot@file_update_time-attribute>`
* :ref:`/NXroot@h5py_version-attribute </NXroot@h5py_version-attribute>`
* :ref:`/NXroot@HDF5_Version-attribute </NXroot@HDF5_Version-attribute>`
* :ref:`/NXroot@HDF_version-attribute </NXroot@HDF_version-attribute>`
* :ref:`/NXroot@NeXus_version-attribute </NXroot@NeXus_version-attribute>`
* :ref:`/NXroot@NX_class-attribute </NXroot@NX_class-attribute>`
* :ref:`/NXroot@XML_version-attribute </NXroot@XML_version-attribute>`

**NXDL Source**:
  https://github.com/nexusformat/definitions/blob/main/base_classes/NXroot.nxdl.xml