NeXus International Advisory Committee

Current Members

See the page with the expiration dates for when the current terms of the various members end and we require a new facility endorsement and vote (see below).

How to contact the NIAC

You may contact the NIAC by sending an email to


Terms of Reference

The purpose of the NeXus International Advisory Committee is to supervise the development and maintenance of the NeXus common data format for neutron, x-ray, and muon science. This purpose includes, but is not limited to, the following activities.

  1. To establish policies concerning the definition, use, and promotion of the NeXus format.
  2. To ensure that the specification of the NeXus format is sufficiently complete and clear for its use in the exchange and archival of neutron, x-ray, and muon data.
  3. To receive and examine all proposed amendments and extensions to the NeXus format. In particular, to ratify proposed application definitions and base classes, to ensure that the data structures conform to the basic NeXus specification, and to ensure that the definitions of data items are clear and unambiguous and conform to accepted scientific usage.
  4. To ensure that documentation of the NeXus format is sufficient, current, and available to potential users both on the internet and in other forms.
  5. To coordinate with the developers of the NeXus Application Programming Interface to ensure that it supports the use of the NeXus format in the neutron, x-ray, and muon communities, and to promote other software development that will benefit users of the NeXus format.
  6. To coordinate with other organizations that maintain and develop related data formats to ensure maximum compatibility.

The committee will meet at least once every calendar year according to the following plan:


The NeXus International Advisory Committee will seek balanced representation of the international community. It will consist of at most one voting representative from each major neutron, synchrotron x-ray, and muon facility. Membership would normally be for a three year renewable term. Members will be nominated by each facility through the facility director and approved by the existing committee. Each member can appoint a substitute to attend a particular meeting.

The committee reserves the right to appoint additional members for a limited period to ensure balanced representation.


Accountability: The NeXus International Advisory Committee will ensure that their decisions are reported both on the NeXus web site and on the NeXus mailing list. Committee business will be conducted either through a mailing list, to which non-committee members can subscribe and whose archive will be available on the web, or through meetings, which will be advertised on the NeXus mailing list and which non-committee members may attend.
The NeXus International Advisory Committee will have the following executive officers:

All of these officers will be elected for a two year term. The incumbent chair and executive secretary are limited to two consecutive terms.

Voting: Only members of the NeXus International Advisory Committee will be able to vote on specific proposals that come under the remit of the committee. However, all debates will be conducted publicly and non-committee members are both allowed and encouraged to participate.

Topics voted on at the biennial NIAC meetings will require a simple majority unless specifically challenged by a committee member. In the event of a challenge, the issue will be presented to the NeXus mailing list inviting comments for a period of one month. At the end of this period, the challenge can be overruled by a two thirds majority.

Voting outside of the biennial NIAC meetings can take two forms. Firstly, memberships can be approved by email ballot. All other issues require a vote that receives responses from at least 2/3 of the NIAC during the following two week voting period. The opening of the voting period must be advertised through the NIAC mailing list. At the close of the voting period, NIAC members who have not responded have abstained (and are not counted towards the 2/3 requirement). Whether the issue involved is membership or any other issue, the NIAC decision shall be determined by whatever outcome receives the most votes that are not abstentions, i.e. the outcome which receives more votes than any other outcome other than abstention, even if the chosen outcome does not receive an absolute majority of the votes.

The constitution can only be changed by a two thirds majority of the NIAC.

Special Interest Groups: The NeXus International Advisory Committee will appoint editors to be in charge of particular groups that wish to specify instrument definitions or develop specialized uses of the NeXus format. The groups will establish their own mode of operation, but will be expected to consult widely with the community relevant to their work, and to refer back to the NeXus International Advisory Committee any matters that involve a change in the current NeXus specification. Specific proposals produced by these groups will be presented to the NeXus International Advisory Committee for comment and formal ratification.


NIAC Decisions sorted by Topic

This is a collection of past NIAC decisions sorted by topic. This serves mainly as a reference for NIAC members, hence the recording is rather terse and not meant for consumption on it’s own.

Action Items

Action Items for members of the NIAC that are not associated to one of the repositories.


The former NeXus Technical sub-committee that used to host regular teleconference meetings has been retired. In the interest of being inclusive and approachable the sessions are now open to all interested parties. See the Teleconferences page for agendas, minutes, and how to join.