A general metadata standard for describing a wide range of digital resources. The documentation on the 15 Dublin Core Metadata Element is available at: https://www.dublincore.org/specifications/dublin-core/dcmi-terms/
The Global Information Locator Service defines a core element set for government information so that it can be more searchable and discoverable by the general public. Details can be found at: https://www.ntsb.gov/GILS/Pages/FAQ.aspx
Categories for the Description of Works of Art (CDWA): a conceptual framework and guidelines for the description of art objects and images. Its site is at: http://www.getty.edu/research/publications/electronic_publications/cdwa/index.html.
MPEG-7: The Multimedia Content Description Interface MPEG-7 is an ISO/IEC standard and specifies a set of descriptors to describe various types of multimedia information and is developed by the Moving Picture Experts Group. It is available at: http://mpeg.chiariglione.org/standards/mpeg-7/mpeg-7.htm.
NISO Metadata for Digital Images: This standard defines a set of metadata elements for raster digital images to enable 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. For details, please refer to https://www.niso.org/publications/ansiniso-z3987-2006-r2017-data-dictionary-technical-metadata-digital-still-images.
Visual Resources Association Core Categories (VRA): a data standard for the description of works of visual culture as well as the images that document them. Its website is at: http://www.loc.gov/standards/vracore/.
PBCore: the metadata standard for audiovisual media developed by the public broadcasting community. Its official website is at: http://pbcore.org/.