DCMI, Elements, Robots, APEX RDF Schema Implementation (Links open onsite in a new window)
The concepts behind meta data have been used by librarians for generations. Metadata, information about a document's content, brings the power of a database to electronic documents. Just as you could search for an item using the title, subject, or author in the library card catalog, you can search for electronic documents using an unlimited number of fields, or meta tags.
Metadata is stored within a document. Although you cannot see it when you open the file using an information browser, metadata remains inside a file no matter where the file moves. Meta data works with any file formats and media types, requires minimal user interaction, and employs universal bibliographic standards. Robert B.Yonaitis of Hiawatha Island Software Company explains that with metadata, "People can find and retrieve the information they need without changing the way they work."
In fact there is one metadata-based general purpose lookup facility: Yahoo! Yahoo doesn't use a robot. When you search through Yahoo, you're searching through human-generated subject categories and site labels. Compared to the amount of metadata that a library maintains for its books, Yahoo! falls very short; but its popularity is clear evidence of the power of (even limited) metadata.
The term "meta" derives from the Greek word denoting a nature of a higher order or more fundamental kind. A metadata record consists of a number of pre-defined elements representing specific attributes of a resource, and each element can have one or more values.
There are literally hundreds of metadata schemas to choose from and the number is growing rapidly, as different communities seek to meet the specific needs of their members. Selecting which schema fits your particular needs can be a daunting task.