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The term "Metadata" was first created by Philip Bagley in 1968, in his book Extension of programming language concepts. Since then the fields of information management, information technology, information science, librarianship and GIS have widely adopted this term.

What is Metadata?

To be brief and simple, metadata is "data about data", defined by OCLC (Online Computer Library Center) and NCSA (National Center of Supercomputing Applications). To be precisely, metadata is structured information that describes, explains, locates, or otherwise make it easier to retrieve, use, or manage an information resource.

Metadata has been applied in many fields, and each of which has a unique definition of metadata. So there isn't an agreed definition that describes all kinds of metadata used in every field.

card cataloge of a book

Here's an example of simple metadata, a card catalog of a book in past days. There are author, title, subtitle, publisher, date of publication, place of publication, etc. All data about a book, which is also data.

Now we mostly focus on metadata in digital format and web resources.


There are three basic types of metadata, sorted by NISO (National Information Standards Organization).

  • Structural Metadata - data about containers of data
This is actually what Philip meant when he first mentioned the word "metadata".
Structural metadata shows how compound objects are put together.
e.g. How pages are ordered to form chapters.
Structural metadata often means the inner order, structure, schema of data.

  • Descriptive Metadata - data about data content
This is the type of metadata which is the most similar to the definition of "data about data".
Descriptive metadata means a resource for purpose such as discovery and identification.
e.g. title, abstract, author, keyword, publisher, etc.

  • Administrative Metadata - provides information to help manage a resource
e.g. when and how it was created, location, who has the authority to access, file type, etc.

What does metadata do?

  • Discovery and identification
Metadata helps people retrieve and identify resources.
Usually these metadata includes but not limits to, author, title, date, keyword, and other simple information.
  • Cataloging
Metadata helps people catalog and describe data cell.
These metadata often includes many information of the data, such as contents, carriers, location, etc.
  • Resource administration
Metadata helps people manage, store and use information.
Besides cataloging information, these metadata also includes right/Privacy management, Digital signature, Seal of Approval/Rating, Access management, Payment and accounting, etc.
  • Preservation and Archiving
Metadata helps support long-term preservation for resources.
Besides the description and identification of resources, these metadata also includes specific information of format, creation, migration methods, etc.

Metadata standards

Standard Focus
DDI Archiving and Social Science
EAD Archiving
CDWA/VRA Core Arts
Darwin Core Biology
ONIX Book industry
CWM Data warehousing
EML Ecology
IEEE LOM Education
CSDGM / ISO 19115 Geographic data
e-GMS Government
GILS Government/Organizations
TEI Humanities, social science and linguistics
<indecs> Intellectual property
PBCore Media
MPEG-7 Multimedia
MEI Music notation
Dublin Core/DOI Networked resources
ISO/IEC 1179 Organizations
ISO/IEC 19506 Software system
ISO 23081/MoReq2010 Records management
DIF Scientific data sets
RDF Web resources

(seen in wikipedia - metadata standards)

Dublin Core

Also known as DCMI, stands for Cublin Core Metadata Initiative.

Dublin Core is the most common standard both for digital libraries and web sources.

Dubin Core is a set of vocabulary terms which can be used to describe resources for the purposes of discovery.

  • Title
  • Creator
  • Subject and keyword
  • Description
  • Publisher
  • Contributor
  • Date
  • Type
  • Format
  • Identifier
  • Source
  • Language
  • Relation
  • Coverage
  • Rights

There's a simple example of metadata based on Dublin Core:

 Title=”Metadata Demystified”
 Creator=”Brand, Amy”
 Creator=”Daly, Frank”
 Creator=”Meyers, Barbara”
 Description=”Presents an overview of metadata conventions in publishing.”
 Publisher=”NISO Press”
 Publisher=”The Sheridan Press”

(NISO, understanding metadata, 2004)

Syntax Structure

A single metadata document could be expressed in one or a few different kinds of markup and programming languages, each in different grammar and syntax.

XML is one of the most common format of metadata, among which, RDF(The Resource description Framework) has been used as a well-known language.

Here's an example of RDF:

 <RDF xmlns="" 
 <Description about="">
 <dc:title>The W3C Folio 1999</dc:title> 
 <dc:creator>W3C Communications Team</dc:creator> 
 <dc:subject>Web development, World Wide Web Consortium, Interoperability of the Web</dc:subject> 

(W3C, Metadata Activity Statement)


Wikipedia - Metadata
Wikipedia - Metadata Standards
NISO. 2004. Understanding Metadata
W3C - Metadata Activity
Baidu Baike - Metadata

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