Saturday, 26 March 2011


Metadata (metacontent) is defined as data providing information about one or more aspects of the data, such as:

    * Means of creation of the data
    * Purpose of the data
    * Time and date of creation
    * Creator or author of data
    * Placement on a computer network where the data was created
    * Standards used

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.

Metadata is data. As such, metadata can be stored and managed in a database, often called a registry or repository. However, it is impossible to identify metadata just by looking at it because a user would not know when data is metadata or just data.[1]

Metadata has been used in various forms as a means of cataloging archived information. The Dewey Decimal System employed by libraries for the classification of library materials is an early example of metadata usage. Library catalogues used 3x5 inch cards to display a book's title, author, subject matter, and a brief plot synopsis along with an abbreviated alpha-numeric identification system which indicated the physical location of the book within the library's shelves. Such data helps classify, aggregate, identify, and locate a particular book. Another form of older metadata collection is the use by US Census Bureau of what is known as the "Long Form." The Long Form asks questions that are used to create demographic data to create patterns and to find patterns of distribution. [2] The term was coined in 1968 by Philip Bagley, one of the pioneers of computerized document retrieval.[3][4] 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".[5] While this is the generally accepted definition, various disciplines have adopted their own more specific explanation and uses of the term.

For the purposes of this article, an "object" refers to any of the following:

    * A physical item such as a book, CD, DVD, map, chair, table, flower pot, etc.
    * An electronic file such as a digital image, digital photo, document, program file, database table, etc.


Metadata may be written into a digital photo file that will identify who owns it, copyright & contact information, what camera created the file, along with exposure information and descriptive information such as keywords about the photo, making the file searchable on the computer and/or the Internet. Some metadata is written by the camera and some is input by the photographer and/or software after downloading to a computer.

Photographic Metadata Standards are governed by organizations that develop the following standards. They include, but are not limited to:

    * IPTC Information Interchange Model IIM (International Press Telecommunications Council),
    * IPTC Core Schema for XMP
    * XMP – Extensible Metadata Platform (an Adobe standard)
    * Exif – Exchangeable image file format, Maintained by CIPA (Camera & Imaging Products Association) and published by JEITA (Japan Electronics and Information Technology Industries Association)
    * Dublin Core (Dublin Core Metadata Initiative – DCMI)
    * PLUS (Picture Licensing Universal System)


Metadata is particularly useful in video, where information about its contents (such as transcripts of conversations and text descriptions of its scenes) are not directly understandable by a computer, but where efficient search is desirable.
Web pages

Web pages often include metadata in the form of meta tags. Description and keywords meta tags are commonly used to describe the Web page's content. Most search engines use this data when adding pages to their search index.
Creation of metadata

Metadata can be created either by automated information processing or by manual work. Elementary metadata captured by computers can include information about when a file was created, who created it, when it was last updated, file size and file extension.

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