Prudens Information Resources for the Internet


Knowledge Representation & Search

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What is Metadata? | Dublin Core Metadata | Other Metadata Systems | Other Useful Metadata Sites | References

What is Metadata?

Metadata are information about information and are encountered everyday when one searches for information. The yellow pages, the card catalog at the library, and a book index are examples of metadata. Metadata are obviously very useful. (See the e-Report The Semantic Web for a further description of metadata)

Many forms of metadata are found on the web with the most prevalent being the Dublin Core Metadata. One problem of machine readable metadata is that the different systems aren't interoperable - the metadata from one system can't be read by another. Also, each metadata system is usually designed for a different purpose, and contains different types of information. This is a problem, often not recognized, in developing categories of information in general, and in establishing a taxonomy of the types of information used in a metadata system, in particular.

Metadata systems are often described in terms of semantics and syntax. Semantics refer to the names and meanings of the metadata elements. Syntax refers to the rules for the encoding of the metadata elements and their content. These are shown in the following paragraphs.

Dublin Core Metadata

The Dublin Core Metadata Initiative ( is a general metadata system, which describes a range of information and content sources on the Web in a concise and easy manner. Its 15 elements can be repeated, omitted, or placed in any order to describe an electronic object, usually an electronic document. It has been adopted as a standard by the American National Standards Institute (ANSI) and the National Information Standards Institute (NISO) (see ANSI/NISO Z39.85-2001).

The 15 elements of the Dublin Core are:

Because of its ease of use the Dublin Core metadata system has been widely adopted. Yet it suffers from the criticism that it carries insufficient detail for use in the web publishing industry, or in the archiving of electronic documents compared to other metadata systems.

Other Metadata Systems

Other more specific metadata systems have been developed for specific types of applications. Examples are:

Other Useful Metadata Sites


Dr. James E. Burke is a Principal in Burke Technology Services (BTS). BTS provides business assistance to startup technology companies, or organizations planning or integrating new technologies; develops and manages technology projects; performs technology evaluation and commercialization, and assists in technology-based economic development.

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