The now anachronistic library card catalog is an example of metadata. Other examples of metadata include web indexes, descriptions of archeological artifacts, and annotated bibliographies. Metadata, or descriptions of data, allow information users to search rapidly and accurately for the items connected to the metadata. Sifting through thousands of volumes would be an ineffective way to search for a particular book. Metadata allows the user to search for items rapidly and in an organized fashion.
Metadata can employ controlled vocabulary or natural language techniques.
The ubiquitous presence of the Internet has raised a number of questions about the practicality of metadata. Search engines return unwieldy numbers of documents in no particular order. Relevance, authority, and even coherence are obscured by the chaos of web sites retrieved. Often the same web site is listed repeatedly ad nauseum, and an information-seeker must wade through pages of links to discover a less popular or infrequently advertised site. Librarians and subject specialists have created a number of metadata standards for describing electronic resources.