Metadata is “data that provides information about other data,” but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including:
- Descriptive metadata – the descriptive information about a resource. It is used for discovery and identification. It includes elements such as title, abstract, author, and keywords.
- Structural metadata – metadata about containers of data indicates how compound objects are put together, for example, how pages are ordered to form chapters. It describes the types, versions, relationships, and other characteristics of digital materials.
- Administrative metadata – the information to help manage a resource, like a resource type, permissions, and when and how it was created.
- Reference metadata – the information about the contents and quality of statistical data.
- Statistical metadata, also called process data, may describe processes that collect, process or produce statistical data.
- Legal metadata – provides information about the creator, copyright holder, and public licensing, if provided.
Metadata is not strictly bound to one of these categories, as it can describe a piece of data in many other ways.
Metadata has various purposes. It can help users find relevant information and discover resources. It can also help organize electronic resources, provide digital identification, and archive and preserve resources. Metadata allows users to access resources by “allowing resources to be found by relevant criteria, identifying resources, bringing similar resources together, distinguishing dissimilar resources, and giving location information.” Metadata of telecommunication activities, including Internet traffic, is widely collected by various national governmental organizations. This data is used for traffic analysis and can be used for mass surveillance.
Metadata was traditionally used in the card catalogs of libraries until the 1980s, when libraries converted their catalog data to digital databases. In the 2000s, as data and information were increasingly stored digitally, these digital data were described using metadata standards.
The first description of “metadata” for computer systems is purportedly noted by MIT’s Center for International Studies experts David Griffel and Stuart McIntosh in 1967: “In summary then, we have statements in an object language about subject descriptions of data and token codes for the data. We also have statements in a meta language describing the data relationships and transformations, and ought/is relations between norm and data.”
Unique metadata standards exist for different disciplines (e.g., museum collections, digital audio files, websites, etc.). Describing the contents and context of data or data files increases its usefulness. For example, a web page may include metadata specifying what software language the page is written in (e.g., HTML), what tools were used to create it, what subjects the page is about, and where to find more information about the subject. This metadata can automatically improve the reader’s experience and make it easier for users to find the web page online. A CD may include metadata about the musicians, singers, and songwriters whose work appears on the disc.
In many countries, government organizations routinely store metadata about emails, telephone calls, web pages, video traffic, IP connections, and cell phone locations.
Definition
Metadata means “data about data.” Metadata is the data providing information about one or more aspects of the data; it is used to summarize basic information about data that can make tracking and working with specific data more accessible. Some examples include:
- Means of creation of the data
- Purpose of the data
- Time and date of creation
- Creator or author of the data
- Location on a computer network where the data was created
- Standards used
- File size
- Data quality
- Source of the data
- The process used to create the data
For example, a digital image may include metadata describing the image’s size, color depth, resolution, when it was created, shutter speed, and other data. A text document’s metadata may contain information about how long the document is, the author’s name, when the document was written, and a summary. Metadata within web pages can also contain descriptions of page content and keywords linked to the content. These links are often called “Metatags,” which were used as the primary factor in determining an order for a web search until the late 1990s. The reliance on metatags in web searches decreased in the late 1990s because of “keyword stuffing,” whereby metatags were being largely misused to trick search engines into thinking some websites had more relevance in the search than they did.
Metadata can be stored and managed in a database, often called a metadata registry or repository. However, without context and a point of reference, it might be impossible to identify metadata just by looking at it. For example: by itself, a database containing several numbers, all 13 digits long, could be the results of calculations or a list of numbers to plug into an equation — without any other context, the numbers themselves can be perceived as the data. But if given the context that this database is a log of a book collection, those 13-digit numbers may now be identified as ISBNs — information that refers to the book but is not itself the information within the book. The term “metadata” was coined in 1968 by Philip Bagley in his book “Extension of Programming Language Concepts” where it is clear that he uses the term in the ISO 11179 “traditional” sense, which is “structural metadata,” i.e., “data about the containers of data”; rather than the alternative sense “content about individual instances of data content” or meta content, the type of data usually found in library catalogs. Since then, the fields of information management, information science, information technology, librarianship, and GIS have widely adopted the term. The word metadata is defined in these fields as “data about data.” While this is the generally accepted definition, various disciplines have adopted a more specific explanation and use of the term.
Slate reported in 2013 that the United States government’s interpretation of “metadata” could be broad and include message content such as the subject lines of emails.
