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The 6 core metadata schemas explained
11th January 2024
Metadata is at the heart of Digital Asset Management (DAM). It allows almost limitless categorisation of assets and drives the intuitive search functionality that makes a DAM so much more powerful than simple file storage solutions.
However, without a clearly defined structure, it can become very difficult to effectively manage the DAM and control how assets are uploaded and categorised.
This is where your metadata schema comes in.
The metadata schema outlines an overall structure for the metadata. This includes how the metadata is set up and usually includes typical fields, such as dates, names and places.
In this article we’re going to explore six of the most common metadata schemas.
International Press Telecommunications Council (IPTC) Metadata Standard
Widely recognized and deeply integrated into the fabric of digital asset management, especially in the realm of photography, is the IPTC Metadata Standard. This standard is maintained by the International Press Telecommunications Council (IPTC), a consortium of the world's major news agencies, news publishers, and news industry vendors.
The IPTC standard excels in embedding a comprehensive range of metadata directly into digital images. This embedded information can include critical elements such as captions, keywords, photographer credits, copyright details, and extensive descriptive information. Such rich metadata content is essential for professionals in media, journalism, and photography, where accurate and immediate data retrieval is crucial.
The core components of the IPTC metadata standard are:
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IPTC Core Schema: Includes basic metadata properties commonly used by photographers and photo editors, such as title, description, keywords, creator, copyright information, and usage rights.
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IPTC Extension Schema: Expands on the Core schema by adding more detailed information like location data, model and property release status, and additional administrative details.
One of the key strengths of IPTC metadata is its wide acceptance and integration into numerous photo editing and digital asset management tools. This ubiquity allows for a seamless workflow, where photographers and editors can tag and manage assets efficiently within their preferred software environments.
Moreover, IPTC metadata often includes Dublin Core elements, showcasing its compatibility and flexibility with other metadata standards. This interoperability enhances its functionality within a broader range of systems and platforms.
IPTC's impact is profound - it's not an exaggeration to say that billions of digital assets are marked up with IPTC metadata. Its widespread usage underlines its critical role in the categorization, searchability, and management of photographic content. While it holds a particular sway in the media and photography sectors, its influence extends to various digital asset management scenarios, making it a cornerstone in the world of metadata standards.
Dublin Core Metadata Initiative (DCMI)
Formerly known as the Dublin Core Metadata Element Set, Dublin Core is an international metadata schema maintained by the Dublin Core Metadata Initiative (DMCI), an independent, public and nonprofit organisation. The Dublin Core schema is generally used to describe digital and physical resources.
DCMI consists of 15 elements (known as the Dublin Core Metadata Element Set) alongside ‘extension vocabularies’, which include dozens of properties, classes, data types and vocabulary encoding schemes.
Note that there are two forms of Dublin Core:
- Simple Dublin Core, which expresses elements as attribute-value pairs using the 15 metadata elements of the Dublin Core Metadata Element Set.
- Qualified Dublin Core, which adds information about encoding schemes, enumerated lists and other processing elements that increase the specificity of metadata that helps with searches, for example within a DAM. However, this additional complexity can create interoperability challenges.
The 15 metadata elements in Simple Dublin Core are:
- Title
- Creator
- Subject
- Description
- Publisher
- Contributor
- Date
- Type
- Format
- Identifier
- Source
- Language
- Relation
- Coverage
- Rights
The original Dublin Core was first published in 1995, and over the years it has become an ISO standard.
Metadata Encoding & Transmission Standard (METS)
The Metadata Encoding & Transmission Standard (METS) schema is designed specifically for objects within a digital library. It’s a standard test for encoding descriptive, administrative and structural metadata.
Expressed using the W3C’s XML schema—a language used to specify the structure of an XML document—METS is maintained by the METS Board in collaboration with the Network Development and MARC Standards Office of the Library of Congress.
The use cases of METS includes:
- Creating XML document instances that express the hierarchical structure of digital library objects.
- Recording names and locations of digital library object files.
- Recording metadata associated with digital library objects.
Metadata Object Description Schema (MODS)
Like METS, the Metadata Object Description Schema (MODS) is maintained by the Network Development and MARC Standards Office of the Library of Congress.
MODS is an XML-based schema for a blibiographic element set used for library applications, but that may be used for a variety of other purposes. It was designed to be a compromise between the simplicity of the Dublin Core metadata standard and the complexity of the MARC format used by libraries. The MODS record carries key data elements from the MARC record, but it does not define all of the MARC fields.
Because MODS is less complex than MARC, it offers high compatibility with existing resource descriptions and various internal record element sets can be mapped to it, including the Dublin Core Metadata Element Set (version 1.1). An example use case of this mapping would be to conduct OAI (Open Archives Initiative) harvesting in Dublin Core syntax of MODS records. The purpose of this harvesting is to build services using metadata from the MODS archive.
Text Encoding Initiative (TEI)
As the name suggests, the Text Encoding Initiative (TEI) develops and maintains a standard for text in digital forms, including a set of guidelines for specifying encoding methods for machine-readable texts, specifically in the humanities, social sciences and linguistics sectors.
Published for the first time in 1994, the TEI guidelines have been used by libraries, museums, publishers and scholars to present texts for online research, preservation and teaching.
The guidelines define hundreds of elements and attributes for marking up documents, with each definition including:
- A description
- A formal declaration
- Usage examples
Visual Resources Association (VRA) Core
Another metadata schema maintained by the Network Development and MARC Standards Office of the Library of Congress (in association with the Visual Resources Association), the Visual Resources Association (VRA) Core is used for describing ‘works of visual culture’ and the images that document them. Works of visual culture include both objects and events, such as paintings, drawings, sculptures, architecture, photographs, books and performance art.
The VRA Core is loosely based on the Dublin Core, and has grown from an original list of elements describing art and architectural images to a full data standard for describing images. The latest iteration (Core 4) is the only metadata schema designed specifically for describing images and related cultural objects.
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