metadata

metadata, data about informational aspects of other data. For example, the date and time of a text message is metadata, but the text of that message is not. The term metadata is a portmanteau of data and meta- (in the word’s epistemological sense of “about”).

Metadata allows for the easy retrieval, management, and use of data. It can be collected for any type of data, from the content of ancient scrolls to that of modern websites, and it can relate to any informational aspect of data, such as its origin, location, format, or quality. Metadata can also be cataloged and referenced in any medium, but, because the word originated in the field of computer science, it is primarily associated with computers. The term has therefore grown more common over time as practitioners of other disciplines have integrated computers into their work. Now, even members of industries and academic fields that dealt with a great amount of information prior to the arrival of computers, such as libraries and publishers, often refer to metadata.

To be a useful reference, metadata is—or at least ought to be—structured to model the most important features of the data it describes. The standard digital record kept by libraries, for instance, identifies an item’s author, title, subject, and call number. As different industries and academic fields have learned to digitally track their data, each one has either adopted or created its own metadata standard, that is, a document establishing the structure of its metadata. These standards are maintained and updated by various governing bodies, some of which are wholly dedicated to that work, e.g., the International Organization for Standardization (ISO), and some of which oversee standards as part of their larger mission, as with the European Broadcasting Union. The International Press Telecommunications Council (IPTC) has had an outsized influence on the systemization of metadata. In 1979 the IPTC became one of the first organizations to publish a metadata standard by listing and defining what metadata could be placed in images. In the 1990s the IPTC followed up on this early work by releasing the Information Interchange Model (IIM), a file structure for information about text, pictures, and other media. Starting in 1994, Adobe Systems made it possible to include the metadata of a computer file, such as an image, as part of that same file instead of in an adjoining one. Adobe used the IPTC’s metadata definitions when creating these “headers.”

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Adobe went on to further improve the tracking of metadata in 2001 with the introduction of the Extensible Metadata Platform (XMP). Still in use, XMP enables applications and publishing systems to tag digital content with desired metadata at the time of its creation. As an open-source technology capable of accommodating the metadata standards of third parties, the technology soon after its release became a common method of embedding metadata in digital files, and it is now an ISO standard. A plethora of other metadata formats have followed, such as Exchangeable Image File Format (EXIF), which almost all consumer-level digital cameras use to embed metadata in the pictures they take.

These and other improvements to the tracking of metadata have naturally resulted in the development of metadata standards that enable finding Internet resources, such as Dublin Core. The search engine AltaVista can be credited with pioneering the practice of searching the Internet via two simple metadata elements—“descriptions” and “keywords”—that can be embedded in webpages’ head sections using the HTML meta tag. Today, search engines heavily rely on HTML title tags, which are simple pieces of metadata that most Web browsers display in title bars and users’ bookmarks. Metadata has thus become an important component of search engine optimization (SEO) for creators of the vast majority of websites.

The exponentially increased volume of metadata and its relatively new importance has led to legal questions regarding its use. In the Williams v. Sprint/United Mgmt Co. case (2005), a magistrate judge in the United States ruled that all data submitted in the discovery phase of a trial must include relevant metadata. In 2010 the Arizona Supreme Court ruled that the metadata of public records is itself a public record. Edward Snowden’s disclosure in 2013 that intelligence services were harvesting the detailed metadata of millions of citizens’ phone calls resulted in a global uproar. The bulk telephony metadata program was banned with the passage of the USA FREEDOM Act in 2015; in 2020 the 9th Circuit U.S. Court of Appeals ruled that the program was illegal and possibly unconstitutional.