# 3.3.1.44. NXroot¶

Status:

base class, extends NXobject

Description:

Definition of the root NeXus group.

Symbols:

No symbol table
Groups cited:
NXentry

Structure:

@NX_class: (optional) NX_CHAR

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

@file_time: (optional) NX_CHAR

Date and time file was originally created

@file_name: (optional) NX_CHAR

File name of original NeXus file

@file_update_time: (optional) NX_CHAR

Date and time of last file change at close

@NeXus_version: (optional) NX_CHAR

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.

@HDF_version: (optional) NX_CHAR

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

@HDF5_Version: (optional) NX_CHAR

Version of HDF5 library used in writing the file.

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

@XML_version: (optional) NX_CHAR

Version of XML support library used in writing the XML file

@h5py_version: (optional) NX_CHAR

Version of h5py Python package used in writing the file

@creator: (optional) NX_CHAR

facility or program where file originated

@default: (optional) NX_CHAR

Declares which NXentry group contains the data to be shown by default. It is needed to resolve ambiguity when more than one NXentry group exists. The value is the name of the default NXentry group.

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

(entry): (required) NXentry

entries
NXDL Source:
https://github.com/nexusformat/definitions/blob/master/base_classes/NXroot.nxdl.xml