Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Frequently Asked Questions

READ-ONLY SITE MATERIALS: Historical voting TWiki site (2015-2020) ARCHIVED from

Following is a list of frequently asked questions (and answers) about the NIST Interoperability public working group and the associated common data format (CDF) project and issues related to it. The following questions are addressed:

Q: What is the NIST Interoperability public working group?
Q: What is a Common Data Format (CDF)?
Q: Why is a CDF needed?
Q: Why is a CDF needed especially for newer election equipment?
Q: Does the CDF work include security issues in voting?
Q: Who benefits from a CDF?
Q: Can a state or county require CDF capability now in equipment purchases or updates?
Q: When will the CDF project be complete?
Q: My state has already been using Pew's VIP format, how is it different?
Q: How do I join the Interoperability public working group or get more information?

Q: What is the NIST Interoperability public working group?

The NIST Interoperability public working group was formed to produce common data format (CDF) specifications for election equipment. Members participate in teleconferences, meetings, and use e-mail correspondence to systematically analyze current elections operations and produce CDF specifications. The Election Assistance Commission's (EAC) Voluntary Voting System Guidelines (VVSG) will, in its next version underway currently, require use of the CDF specifications by election equipment manufacturers, thus all CDF specifications are freely available to the public.

The Interoperability public working group has active participation from most major U.S. manufacturers, as well as voting system test labs accredited to do federal and state certification of voting systems. Various local and U.S. state election officials and representatives are involved, as well as independent contractors and election experts/analysts.

Q: What is a Common Data Format (CDF)?

Election equipment deals primarily with election data - data about voters, candidates, contests, ballots, and results. A voting system is made up of many different devices, including databases, electronic pollbooks for checking voters into the polls, touch screen devices for electronic voting, optical scanners for scanning marked ballots, and election management systems used also for tabulation of votes. A CDF is simply a format that, for a particular use case, describes the election data and that can be used when importing and exporting election data among the various election equipment so that the export/imports are uniform and interoperable across different voting system manufacturers. The common data format uses XML, the eXtensible Markup Language, which is used commonly throughout IT and in some voting equipment already. In some cases, the common data format uses JSON, for Javascript Object Notation, which can be more space efficient than XML. An example of using XML is as follows, with the data encoded with XML tags that each describe the data, e.g.,

<ContestName> 2012 Presidential, State of West Virginia<Candidate>
<CandidateName>John J. Jones</CandidateName>

Q: Why is a CDF needed?

Today's election equipment generally uses proprietary data formats, thus a device from one manufacturer will not "talk" directly to another device from another manufacturer. To transmit voter data from, say, a database to an election management system, the data may have to be exported into an intermediate format such as a "flat file," and software may have to be used to reformat the file into a format that the election management system can read. Software needs to be built to transform one format to another, and because many systems are generally involved, this has the effect of "locking" states and counties into using the same configuration of equipment they have invested in, because it's too much trouble and expense to move to something newer or more desirable and appropriate. A common data format changes all of this and leads to interoperability among devices and manufacturers. Also see also an earlier paper by an election official on the need for a common data format.

Q: Why is a CDF needed especially for newer election equipment?

A CDF is an enabling technology for election operations that involve use of COTS devices and, without it, newer technologies are much more difficult to interface. With a CDF, electronic voting devices become easier to use, test, analyze, secure, and ultimately, trust that they are functioning correctly. This is increasingly important given that some states now use on-line blank ballot distribution systems or COTS devices such as tablet technology to provide mobile delivery of blank ballots or for electronic pollbooks. Use of COTS devices demands a common format for data that integrates well with common IT standards and development methods.

Q: Does the CDF work include security issues in voting?

Not exactly. The scope of the project is limited to a common data format of election data, which is a foundational "building block" of election equipment. It cannot address election policy or security issues in voting related to, e.g., voter registration or on-line voting.

However, the project anticipates that voting equipment may include the capability to digitally sign and validate CDF files as a means for addressing the integrity of the file contents and establishing where the files originated from. Thus, the format includes data structures based on the W3C 's digital signature work so that, for example, voting equipment could sign exported files and and voting equipment could check imported files for valid signatures and ensure file contents have not changed or that files originated from the appropriate voting equipment.

Q: Who benefits from a CDF?

Everyone does, from voters to election administrators to election equipment manufacturers to election analysts and so on. Since a CDF would allow devices to interoperate with respect to data, election officials could largely dispense with using custom software to link devices and could more easily use devices from any manufacturer supporting the CDF. A CDF may expand the market for voting equipment and permit other manufacturers, especially those who specialize in certain equipment, to enter the market and sell equipment in states where, currently, they are "locked out." Entire voting systems must be certified for use currently, but with interoperability, certifying individual devices would be possible and would make the certification process more flexible and less expensive. Manufacturers supporting the CDF project specifications would be able to compete more easily in the market.

Q: Can a state or county require CDF capability now in equipment purchases or updates?

Yes. NIST and the Interoperability public working group have produced the NIST SP 1500-100 specification for election results reporting, which covers a broad range of pre- and post-election data and that can be required in RFPs and in future voting equipment. Ohio used this format for its 2016 elections and a growing number of other U.S. states are now using or preparing to use this specification. Some states have inserted language into their RFP language to directly require specific CDF specifications such as 1500-100, 1500-101, 1500-102, etc., and other states have included language to require support for the CDF standards once all are complete, e.g., "Upon finalization of voting system uniform data format standards currently under development at the Federal level, Contractor(s) shall work with the State to comply with and implement the uniform data format at an agreed-upon time."

Q: When will the CDF project be complete?

At this time 4 CDF specifications have been developed that address a broad spectrum of the election data that is imported and exported from voting equipment. Additional support for the specifications will be implemented such as additional guidance, implementation tools, and examples. It is expected that new versions of the specifications will be issued as voting equipment changes or new needs arise.

Q: My state has already been using Pew's VIP format, how is it different?

Pew's VIP (Voting Information Project) project, supported by Google, is a valuable service to voters and assists election officials by providing convenient access for voters to information about elections. The new VIP version 5.1 format is virtually identical to the NIST SP 1500-100 format for pre- and post-election data and results. VIP's use case involves pre-election information, thus the specification is used differently than it would be for publishing election results, however the format is, again, the same. See Pew's VIP 5.1 page for more information.

Q: How do I join the CDF project or get more information?

The CDF project very much welcomes participation from U.S. State and local election officials and staff, voting equipment manufacturers and software consultants, election analysts/experts, government officials involved in elections, and other interested parties. See the Interoperability public working group page for information and for joining.

Voting TWiki Archive (2015-2020): read-only, archived wiki site, National Institute of Standards and Technology (NIST)


This page, and related pages, represent archived materials (pages, documents, links, and content) that were produced and/or provided by members of public working groups engaged in collaborative activities to support the development of the Voluntary Voting System Guidelines (VVSG) 2.0. These TWiki activities began in 2015 and continued until early 2020. During that time period, this content was hosted on a Voting TWiki site. That TWiki site was decommissioned in 2020 due to technology migration needs. The TWiki activities that generated this content ceased to operate actively through the TWiki at the time the draft VVSG 2.0 was released, in February of 2020. The historical pages and documents produced there have been archived now in read-only, static form.

  • The archived materials of this TWiki (including pages, documents, links, content) are provided for historical purposes only.
  • They are not actively maintained.
  • They are provided "as is" as a public service.
  • They represent the "work in progress" efforts of a community of volunteer members of public working groups collaborating from late 2015 to February of 2020.
  • These archived materials do not necessarily represent official or peer-reviewed NIST documents nor do they necessarily represent official views or statements of NIST.
  • Unless otherwise stated these materials should be treated as historical, pre-decisional, artifacts of public working group activities only.
  • NIST does not warrant or make any representations regarding the correctness, accuracy, reliability or usefulness of the archived materials.


This wiki was a collaborative website. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these archived TWiki materials. Further, NIST does not endorse any commercial products that may be mentioned in these materials. Archived material on this TWiki site is made available to interested parties for informational and research purposes. Materials were contributed by Participants with the understanding that all contributed material would be publicly available.  Contributions were made by Participants with the understanding that that no copyright or patent right shall be deemed to have been waived by such contribution or disclosure. Any data or information provided is for illustrative purposes only, and does not imply a validation of results by NIST. By selecting external links, users of these materials will be leaving NIST webspace. Links to other websites were provided because they may have information that would be of interest to readers of this TWiki. No inferences should be drawn on account of other sites being referenced, or not referenced, from this page or these materials. There may be other websites or references that are more appropriate for a particular reader's purpose.


Created August 28, 2020, Updated February 5, 2021