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What Is Metadata?
Metadata is structured information that describes, explains, locates, or otherwise makes it easier to retrieve, use, or manage an information resource. Metadata is often called data about data or information about information.
The term metadata is used differently in different communities. Some use it to refer to machine understandable information, while others use it only for records that describe electronic resources. In the library environment, metadata is commonly used for any formal scheme of resource description, applying to any type of object, digital or non-digital. Traditional library cataloging is a form of metadata; MARC 21 and the rule sets used with it, such as AACR2, are metadata standards. Other metadata schemes have been developed to describe various types of textual and non-textual objects including published books, electronic documents, archival finding aids, art objects, educational and training materials, and scientific datasets.
There are three main types of metadata:
- Descriptive metadata describes a resource for purposes such as discovery and identification. It can include elements such as title, abstract, author, and keywords.
- Structural metadata indicates how compound objects are put together, for example, how pages are ordered to form chapters.
- Administrative metadata provides information to help manage a resource, such as when and how it was created, file type and other technical information, and who can access it. There are several subsets of administrative data; two that sometimes are listed as separate metadata types are:
- Rights management metadata, which deals with intellectual property rights, and
- Preservation metadata, which contains information needed to archive and preserve a resource.
Metadata can describe resources at any level of aggregation. It can describe a collection, a single resource, or a component part of a larger resource (for example, a photograph in an article). Just as catalogers make decisions about whether a catalog record should be created for a whole set of volumes or for each particular volume in the set, so the metadata creator makes similar decisions. Metadata can also be used for description at any level of the information model laid out in the IFLA (International Federation of Library Associations and Institutions) "Functional Requirements for Bibliographic Records": work, expression, manifestation, or item. For example, a metadata record could describe a report, a particular edition of the report, or a specific copy of that edition of the report.
Metadata can be embedded in a digital object or it can be stored separately. Metadata is often embedded in HTML documents and in the headers of image files. Storing metadata with the object it describes ensures the metadata will not be lost, obviates problems of linking between data and metadata, and helps ensure that the metadata and object will be updated together. However, it is impossible to embed metadata in some types of objects (for example, artifacts). Also, storing metadata separately can simplify the management of the metadata itself and facilitate search and retrieval. Therefore, metadata is commonly stored in a database system and linked to the objects described.
- "Understanding Metadata," National Information Standards Organization (NISO) http://www.niso.org, ISBN: 1-880124-62-9, 2004 http://www.niso.org/standards/resources/UnderstandingMetadata.pdf
File Name: understanding_metadata2004.pdf
Post Date: February 21, 2005 at 8:00 AM CST; 1400 GMT
NISO, a non-profit association accredited by the American National Standards Institute (ANSI) http://www.ansi.org/, identifies, develops, maintains, and publishes technical standards to manage information in our changing and ever-more digital environment. NISO standards apply both traditional and new technologies to the full range of information-related needs, including retrieval, re-purposing, storage, metadata, and preservation. NISO Standards, information about NISO's activities and membership are featured on the NISO website http://www.niso.org.