Metadata: information describing content

Introduction to Metadata

Metadata is defined as the information that describes and explains data. Metadata means data about data. It provides information about one or more aspects of the data and is used to summarize basic information about data that can make tracking and working with specific data easier.

Some examples of metadata include:

For example, a digital image may include metadata that describes the size of the image, its color depth, resolution, when it was created, the shutter speed, and other data.

Why is metadata important?

Metadata ensures that data is: discoverable, trustworthy, relevant, accessible, secure, and interoperable. Without metadata, a data set is incomprehensible.

Discoverable
Metadata makes data easier to find using a text-based search. Each search result will provide enough context to explain what it is about. Metadata also helps to sort and filter through the search results, thus significantly reducing the time spent in data search and discovery.
Trustworthy
Metadata helps to track the lineage of each asset throughout its lifecycle. Documenting changes to an asset over time makes it easier to verify, validate, and use. For example, it is possible to check for issues whenever changes are made to data and notify the relevant downstream data users.
Relevant
It is essential to know whether the data stored is up-to-date and useful for the data teams. For instance, if no one has accessed a data set in over 120 days, then it is either stale or not discoverable. If it is stale, it can be purged completely.
Accessible
Once the data needed is found, metadata provides details on how to access it — authentication and authorization methods.
Secure
Metadata can be used to trace who accessed or modified a specific data set. It also helps to keep track of the various versions of data and classify data to set up data access controls. This, in turn, ensures the security and integrity of data.
Interoperable
Proper metadata management ensures that the entire tech stack — different systems, platforms, and tools — speaks a common language, thus making the systems interoperable.

Types of Metadata

Major Metadata Categories

Metadata can be classified into 6 types:

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 and 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 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.

Descriptive, Structural, and Administrative Metadata

NISO (USA's National Information Standards Organization) distinguishes three types of metadata: descriptive, structural, and administrative. Descriptive metadataz is typically used for discovery and identification, as information to search and locate an object, such as title, authors, subjects, keywords, and publisher. Structural metadata describes how the components of an object are organized. An example of structural metadata would be how pages are ordered to form chapters of a book. Finally, administrative metadata gives information to help manage the source. Administrative metadata refers to the technical information, such as file type, or when and how the file was created. Two sub-types of administrative metadata are rights management metadata and preservation metadata. Rights management metadata explains intellectual property rights, while preservation metadata contains information to preserve and save a resource.

Active Metadata vs. Passive Metadata

Passive metadata is the technical metadata collected and managed via manual processes.

Active metadata is data that describes data, as well as any actions taken on it. Unlike passive metadata, active metadata is an always-on, intelligent, action-oriented, API-driven system that is open by default.

Dublin Core

Dublin Core Metadata Element Set

The original DCMES Version 1.1 consists of 15 metadata elements, defined this way in the original specification:

Contributor
An entity responsible for making contributions to the resource.
Coverage
The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant.
Creator
An entity primarily responsible for making the resource.
Date
A point or period of time associated with an event in the lifecycle of the resource.
Description
An account of the resource.
Format
The file format, physical medium, or dimensions of the resource.
Identifier
An unambiguous reference to the resource within a given context.
Language
A language of the resource.
Publisher
An entity responsible for making the resource available.
Relation
A related resource.
Rights
Information about rights held in and over the resource.
Source
A related resource from which the described resource is derived.
Subject
The topic of the resource.
Title
A name given to the resource.
Type
The nature or genre of the resource.

Each Dublin Core element is optional and may be repeated. The DCMI has established standard ways to refine elements and encourage the use of encoding and vocabulary schemes. There is no prescribed order in Dublin Core for presenting or using the elements. The Dublin Core became a NISO standards, Z39.85, and IETF RFC 5013 in 2007, ISO 15836 standard in 2009 and is used as a base-level data element set for the description of learning resources in the ISO/IEC 19788-2 Metadata for learning resources (MLR) – Part 2: Dublin Core elements, prepared by the ISO/IEC JTC 1/SC 36.

Full information on element definitions and term relationships can be found in the Dublin Core Metadata Registry.

DCMI Metadata Terms

The DCMI Metadata Terms lists the current set of the Dublin Core vocabulary.[12] This set includes the fifteen terms of the DCMES (in italic), as well as the qualified terms. Each term has a unique URI in the namespace http://purl.org/dc/terms, and all are defined as RDF properties.

  • abstract
  • accessRights
  • accrualMethod
  • accrualPeriodicity
  • accrualPolicy
  • alternative
  • audience
  • available
  • bibliographicCitation
  • conformsTo
  • contributor
  • coverage
  • created
  • creator
  • date
  • dateAccepted
  • dateCopyrighted
  • dateSubmitted
  • description
  • educationLevel
  • extent
  • format
  • hasFormat
  • hasPart
  • hasVersion
  • identifier
  • instructionalMethod
  • isFormatOf
  • isPartOf
  • isReferencedBy
  • isReplacedBy
  • isRequiredBy
  • issued
  • isVersionOf
  • language
  • license
  • mediator
  • medium
  • modified
  • provenance
  • publisher
  • references
  • relation
  • replaces
  • requires
  • rights
  • rightsHolder
  • source
  • spatial
  • subject
  • tableOfContents
  • temporal
  • title
  • type
  • valid