In the 21st century, metadata typically refers to digital forms, but traditional card catalogs contain metadata, with cards holding information about books in a library (author, title, subject, etc.).
Metadata is "data that provides information about other data".[1] In other words, it is "data about data." Many distinct types of metadata exist, including descriptive metadata, structural metadata, administrative metadata,[2] reference metadata and statistical metadata.
Metadata means "data about data". Although the "meta" prefix (from the Greek preposition and prefix μετά-) means "after" or "beyond", it is used to mean "about" in epistemology. Metadata is defined as the data providing information about one or more aspects of the data; it is used to summarize basic information about data which can make tracking and working with specific data easier.[12] 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
Process used to create the 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, the shutter speed, and other data.[13] 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. Metadata within web pages can also contain descriptions of page content, as well as key words linked to the content.[14] These links are often called "Metatags", which were used as the primary factor in determining order for a web search until the late 1990s.[14] The reliance of metatags in web searches was decreased in the late 1990s because of "keyword stuffing".[14] Metatags were being largely misused to trick search engines into thinking some websites had more relevance in the search than they really did.[14]
Metadata can be stored and managed in a database, often called a metadata registry or metadata repository.[15] However, without context and a point of reference, it might be impossible to identify metadata just by looking at it.[16] 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 metacontent, the type of data usually found in library catalogues.[17][18] Since then the fields of information management, information science, information technology, librarianship, and GIS have widely adopted the term. In these fields the word metadata is defined as "data about data".[19][page needed] While this is the generally accepted definition, various disciplines have adopted their own more specific explanation and uses of the term.
