Metadata is descriptive, structural, or administrative information included as part of a digital file, electronic record, or other resource. It often includes information such as the file or resource's title, creator, and structure. Metadata is used to catalog and preserve information. By including keywords and descriptions within the metadata, creators or archivists enable users to search for specific records as well as discover similar ones. Metadata is related to the fields of both computer science and library science, as it combines traditional cataloging methods with new electronic file types and distribution methods.
Often described as data about data, metadata consists of information either embedded in a digital file or stored as a separate record in a database or similar directory. The concept is closely related to the cataloging systems used for centuries in libraries and archives, which typically consist of collections of listings—either physical or, following the advent of computers, digital—that include the title, the creator, and a description of each work or artifact, among other key facts. Metadata is intended to assist people in searching for and retrieving the files or information they seek. Similarly, this data enables archivists and catalogers to ensure that information will be well organized and preserved for future reference.
Metadata is an evolving concept, and the term has consequently been used in various ways by different organizations and in different fields. Considered broadly, metadata can be divided into three areas based on the type of information being preserved. Information such as the title and author of an e-book falls under the classification of descriptive metadata, while data regarding the structure of the e-book—the order of the pages and chapters—is considered structural metadata. Administrative metadata is somewhat more loosely defined but generally includes information regarding when the file was created. This category may also include the subcategories of technical metadata, which concerns file formats and sizes; preservation metadata, which can include information about the file's relationships to other files; and intellectual property rights metadata, which is used to capture copyright information. In other cases, technical, preservation, and intellectual property rights metadata are considered distinct categories.
When an item exists in only physical form, as in the case of physical artifacts and texts that have not been digitized, the metadata for that item is typically stored in a searchable database. When dealing with electronic files and other resources, however, creators and catalogers often embed metadata within the files. In hypertext markup language (HTML) files such websites, metadata is typically embedded in the files through the use of specialized HTML tags. Image, audio, and video files can likewise include embedded metadata, usually added by the creator or, in the case of commercially distributed films or music, the studio or distributor. Some cameras, including many smartphone cameras, automatically embed metadata such as the date, time, and place a photograph was taken in each file they produce. This capability has led to concerns that sensitive personal information could be distributed in the form of metadata without an individual's knowledge or permission, and the use of metadata thus remains a topic of debate among individuals and institutions concerned about privacy.
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