Metadata

What is metadata? Metadata is structured information that describes, explains, locates or otherwise makes it easier to retrieve, use, or manage information resources. Metadata is often called data about data or information about information. It is used to describe data.

For example, a digital image may include metadata that describes how large the picture is, the color depth, the image resolution, when the image was created, and other data. A text document's metadata may contain information about how long the document is, who the author is, when the document was written, and a short summary of the document.

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, 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 ofadministrative data; two of them sometimes are listed as separate metadata types:

Rights management metadata which deals with intellectual property rights.

Preservation metadata which contains information needed to archive and preserve a resource.

Metadata can describe resources at any level. It can describe a collection, a single resource, or a component which is a part of a larger resource (for example, a photograph in an article).

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, eliminates problems of linking between data and metadata, and helps to 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 the search and retrieval. Therefore, metadata is commonly stored in a database system and linked to the objects described.

More about metadata next time...