Metadata Standards
By definition, a standard is "something considered by an authority or by general consent as a basis of comparison; an approved model." (Reference: Dictionary.com) In the context of metadata, a metadata standard is a model to be used for metadata storage, which is approved by a standards organization (i.e. ISO, FGDC). Metadata standards provide for the creation of "formal metadata" with consistent collection criteria, terminology and structure.
Metadata standards specify the kinds of information used to describe data, (content, or descriptive standards), and digital storage models (format standards). A metadata standard may include either content or format standards, or both.
Content standards specify the information required to document a dataset; it is a list or hierarchy of required metadata elements to be included in the metadata description. Content standards include things like the name of the metadata element and a definition for that name.
The "base unit" in a standard is a metadata element. Each metadata element contains specific information which, when combined with the content from other elements, completely describe a data set. A metadata standard is a collection of metadata elements combined with a set of statements that formally express the rules of usage for these elements. This approved model, when implemented by multiple projects, helps ensure common practices across existing projects and helps users develop a sound metadata plan for a new project.
Format standards describe digital storage and structural requirements of metadata. Format standards assure that different software programs are able to read or query the data. Format standards are implemented in file formats such as XML, SGML, NetCDF, and indented text.
By carefully articulating how the metadata elements are named, structured and utilized, metadata standards enable interoperability. This is also useful for users who are developing a new project. Standards can provide very specific information about details such as the range of values to be provided for each element (vocabularies), and how to technically present the metadata (format).
Metadata standards provide for the creation of "formal metadata" with consistent collection criteria, naming and structure. The integration of the content and technical standards concepts allows for consistency in what information is included in a metadata set, the structure that is used to store the metadata, and where the metadata are stored within this structure.
For an interesting discussion of "formal metadata", see the Metadata Challenges presentation by Dr. Sara Graves.