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Technical metadata is used for recording the technical attributes of digital objects that include their production or creation information on the digital capture process, i.e., the hardware and software used to acquire the digital object, file formats for master and derivatives, resolutions, color profiles and so on, that enable the reproduction of digital resources in the future. For this reason technical metadata is categorized as administrative and preservation metadata.
Technical metadata can be included in preservation metadata (PREMIS) or structural metadata (METS). The decision regarding where to add the technical metadata can be made based on the types of technical metadata that should be preserved since METS and PREMIS have different ways of incorporating technical metadata in its schema, as mentioned in Preservation Metadata and Structural Metadata Sections (see sections).
Requirements for technical metadata will differ for various media formats. Regardless of media formats, all technical metadata should include the following information.
There is a standard called textMD that is a XML Schema that details technical metadata for text-based digital objects <http://www.loc.gov/standards/textMD/>. It can be added into both METS (as an extension) and PREMIS. It can be also used as a standalone document.
When using the textMD schema, the technical metadata for text-based digital objects may include:
For digital still image, it is recommended to use the NISO Data Dictionary - Technical Metadata for Digital Still Images at <http://www.niso.org/kst/reports/standards?step=2&gid=None&project_key=b897b0cf3e2ee526252d9f830207b3cc9f3b6c2c>.
The document includes metadata elements important to the management of image files that could be captured automatically from scanner or digital camera software. The elements are based on MIX. <http://www.loc.gov/standards/mix/>
The technical metadata for digital still image may include:
For digital audio files (sound only) the technical metadata for the image quality and the image capture process may include:
For digital multi-media files (including video, sound, and animations) the technical metadata for the image quality and capture process may include the:
Currently most of technical metadata can be captured automatically by digital camera or scanner. Followings are the most commonly used tools and standards used for extracting from or embedding metadata to the digital objects.
JHOVE <http://hul.harvard.edu/jhove/ > provides functions to perform format-specific identification, validation, and characterization of digital objects. JHOVE generates technical metadata about files, usually by extracting information from the files themselves.
Adobe's Extensible Metadata Platform (XMP) is a labeling technology that allows users to embed metadata into the file itself. XMP is used for both descriptive (based on Dublin Core) and administrative metadata.
Exchangeable image file format (Exif) < http://www.exif.org/ > is a specification for the image file format used by digital cameras. Exif data is embedded within the image file itself and can be editable. The metadata tags defined in the Exif standard include, date and time information, camera settings such as the camera model and make, and information that varies with each image such as orientation (rotation), aperture, shutter speed, focal length, metering mode, and ISO speed information. A thumbnail for previewing the picture on the camera's LCD screen, in file managers, or in photo manipulation software, and Descriptions and copyright information can be also captured or added later.
Selected Resources for Technical Metadata
Source for File Format Extension Information:
Additional file formats are listed at:
U.S. National Archives and Administration. Technical Guidelines for Digitizing Archival Materials for Electronic Access: Creation of Production Master Files - Raster Images. (June 2004). Online Edition
California Digital Library
Collaborative Digitization Program (select section on digital imaging)