Metadata principle 6: Good metadata records are objects themselves and therefore should have the qualities of good objects, including authority, authenticity, archivability, persistence, and unique identification.

Because metadata carries information that vouches for the provenance, integrity, and authority of an object, the authority of the metadata itself must be established. "Meta-metadata," or stored information about the metadata, should include the identification of the institution that created it and what standards of completeness and quality were used in its creation. The institution should provide sufficient information to allow the user to assess the veracity of the metadata, including how it was created (automatically or manually) and what standards and vocabularies were used.

The Dublin Core Metadata Initiative proposed but never finalized a simple set of data elements for describing metadata records (http://metadata.net/admin/draft-iannella-admin-01.txt). This was unfortunately called the Administrative Core (or "A-Core"), generating some confusion with the more prevalent understanding of administrative metadata. However, despite the unfinished and unapproved nature of the work, some implementers have found it useful.

Some metadata schemes include within them sets of metadata elements for describing the metadata records themselves. These include the IEEE LOM (in the section called "meta-metadata"), the EAD (in "eadheader"), and MODS (in "recordInfo").

The problem of non-authentic and inaccurate metadata is real and serious. Many Internet search engines deliberately avoid using metadata embedded in HTML pages because of pervasive problems with spoofing (one organization supplying misleading metadata for a resource belonging to another organization) and spamming (artificially repeating keywords to boost a page's ranking). The same techniques used to verify the integrity and authenticity of digital documents (e.g. digital signatures) can also be applied to metadata.

Metadata should be documented in a registry that provides standardized information for the definition, identification, and use of each data element. A registry defines metadata characteristics and formatting requirements to ensure that a metadata schema and data elements in use by one organization can be applied consistently within the organization or community, reused by other communities, and interpreted by computer applications and human users. The ISO 11179 metadata registry standard, particularly part 3, Basic attributes of data elements, provides for the consistent definition, interpretation, and use of data elements. Core requirements of ISO 11179-3 include: data element name, data element label, data type, data element identifier and version number, repeatability, obligation for use (e.g., mandatory or optional), controlled vocabulary, and the context or information domain of use.

• A prototype registry is under development by the Dublin Core Metadata Initiative. http://dublincore.org/groups/registry/index2.shtml
• The Moving Image Collections (MIC) project utilizes a simple 11179 registry to document the MIC union catalog core data element set (http://gondolin.rutgers.edu/MIC/text/how/unioncat_registry_table_04_23.htm) and the moving image organizations directory database (http://gondolin.rutgers.edu/MIC/text/how/mic_directory_version_one.htm).

Metadata schemes should also be documented in a syntax that provides guidance and validation for metadata records creation. An XML (eXtensible Markup Language) schema (http://www.w3.org/XML/Schema) provides a structured syntax for indicating whether data elements are mandatory, the sources of the controlled vocabularies or the formatting principles used to create the information that populates the data element, and the relationship between data elements. The XML schema can be used to validate that metadata records have been created properly, which is critical for sharing metadata across organizations and for ensuring that applications that use the organization's metadata, such as search engines, can correctly and consistently interpret and use the metadata. XML Document Type Definitions (DTDs) can also be used to provide standardization and validation of metadata information (http://www.w3schools.com/dtd/default.asp).

Source: adapted from 'A Framework of Guidance for Building Good Digital Collections', published by the National Information Standards Office, 2nd edition, 2004.