An XML Schema and accompanying Data Dictionary -- Technical Metadata for Digital Still Images has been published by the [US] National Information Standards Organization (NISO) and AIIM International for 18-month review as a Draft Standard for Trial Use. A NISO 'Draft Standard for Trial Use (DSFTU)' is typically released when there is a need for field experience before proceeding with balloting; the extended time period "allows implementers to test the standard; at the end of the trial period the standard may be balloted, revised or withdrawn." The data dictionary "defines a standard set of metadata elements for digital images. Standardizing the information allows users to develop, exchange, and interpret digital image files. The dictionary has been designed to facilitate interoperability between systems, services, and software as well as to support the long-term management of and continuing access to digital image collections." An (informative) Annex A presents the MIX Z39.87 XML schema under the name 'NISO Metadata for Images in XML (NISO MIX).' This XML schema "supplies a set of technical data elements required to manage digital image collections; the schema provides a format for interchange and/or storage of the data specified in the dictionary."

Bibliographic information: Data Dictionary -- Technical Metadata for Digital Still Images. Developed by the National Information Standards Organization and AIIM International. Status: Released as a Draft Standard for Trial Use [18 months], June 1, 2002 - December 31, 2003. References: NISO Z39.87-2002 and AIIM 20-2002. 61 pages. "Distribution of this draft standard for comment shall not continue beyond 18 months from the date of publication. It is expected that following this 18 month period, this draft standard, revised as necessary, will be submitted to the American National Standards Institute for approval as an American National Standard. Suggestions for revision should be directed to NISO."

The NISO/AIIM specification makes reference to (Adobe) TIFF, TIFF/EP (ISO/DIS 12234-2), and the DIG35 Working Group's Metadata for Digital Images. "The DIG35 specification distinguishes itself from file format specifications with its stated purpose to facilitate metadata sharing."

"The Library of Congress' Network Development and MARC Standards Office, in partnership with the NISO Technical Metadata for Digital Still Images Standards Committee and other interested experts, is developing an XML schema for a set of technical data elements required to manage digital image collections. The schema provides a format for interchange and/or storage of the data specified in the NISO Draft Standard Data Dictionary: Technical Metadata for Digital Still Images (Version 1.2). This schema is currently in draft status and is being referred to as 'NISO Metadata for Images in XML (NISO MIX)'. MIX is expressed using the XML schema language of the World Wide Web Consortium. MIX is maintained for NISO by the Network Development and MARC Standards Office of the Library of Congress with input from users..." [from the NISO MIX web page]

From the statement of Purpose and Scope:

The purpose of this data dictionary is to define a standard set of metadata elements for digital images. Standardizing the information allows users to develop, exchange, and interpret digital image files. The dictionary has been designed to facilitate interoperability between systems, services, and software as well as to support the long-term management of and continuing access to digital image collections.

This data dictionary presents a comprehensive list of technical data elements relevant to the management of digital still images. In this context, 'management' refers to the tasks and operations needed to support image quality assessment and image data processing throughout the image life cycle. 'Quality assessment' is defined broadly, as it refers both to machine operations and curatorial evaluations. Technical metadata have been identified to 'anchor' meaningful attributes of image quality that can be measured objectively, such as detail, tone, color, and size.

This standard frequently refers to images maintained in TIFF (Tagged Image File Format). The TIFF format is a highly flexible and platform-independent format that is supported by numerous image processing applications. The TIFF specification is publicly available to all users. The structure of the header includes a rich set of technical information important for long-term retention such as for colorimetry, calibration, gamut tables, etc. The information is also very useful for remote sensing and multispectral applications. The repeated references to and examples citing the TIFF format within this standard can be extended to other file formats. The technical dictionary indicates the information and metadata all image files should contain as well as additional information related to image production.

Initial project goals were formed by a NISO/CLIR/RLG Workshop, whose participants "agreed that technical metadata is necessary to support two fundamental goals: to document image provenance and history (production metadata); and to ensure that image data will be rendered accurately on output (to screen, print, or film). Several participants also observed that ongoing management, or 'preservation,' of these core functions will require the development of applications to validate, process, refresh, and migrate image data against criteria encoded as technical metadata." [From the Foreword]