Image Metadata – what is it?
Metadata is best described as ‘data about data’. In terms of image metadata, it is data about visual objects and their digital surrogates. For metadata to be meaningful, consistent and to promote interoperability, it has to be standardised.
These three metadata standards make up a metadata schema:
Data Structure – also known as ‘data standards’ , ‘element sets’, or ‘fields’ which are created to describe the object, examples of these are:
- VRA Core 4.0: a data standard developed by the Visual Resources Association for the cultural heritage community to describe works of art and their digital surrogates.
- (CDWA) Categories for the description of Works of Art: a data standard first created in the early 1990’s, to describe works of art, architecture, groups of objects, and visual and textual objects.
- Dublin Core: a data standard created to describe a range of born digital assets, not specifically visual, but which is often used to map to different standards.
Data content Rules – guidance in formatting the data values/contents of field elements, such as:
- (CCO) Cataloguing Cultural Objects, specifically designed for the cultural heritage community.
Data values/controlled vocabularies – authority files of controlled vocabulary terms recommended for describing works of art and their surrogates, examples include:
- The Getty Vocabularies which are recommended for the cultural heritage community, and are made up of (AAT) The Art and Architecture Thesaurus, (ULAN) Union List of Artists Names, (TGN) Thesaurus of Geographic Names and (CONA) The Cultural Objects Name Authority.
- (LCSH) Library of Congress Subject Headings a controlled vocabulary file mainly used bibliographic cataloguing.
- (LCTGM) Library of congress Thesaurus for Graphic Materials a subject index for pictorial materials.
- ICONCLASS a classification system designed for art and iconography.
- (MLA) Modern Language Association a language style for documentation of the humanities subjects.
- Grove Dictionary of Art a subscription accessed online dictionary of art history terms, also available in published format.
ACADI members’ metadata element sets:
University College Falmouth – ‘The Image Space’, based on VRA Core 4.0:
Creator (changed from ‘Agent’): Name assigned to an individual, group, or corporate body who has contributed to the design, creation, production, manufacture or alteration of the Work or Image. Data values: ULAN & LCNAF
Creator Dates: Dates associated with the creator’s life, including earliest and latest date. For living artists, use the value present in the latest date sub-element, for example: ‘1939-present’. Data values: ISO 8601 standards.
Title: Title of identifying phrase given to a work. Data values: formulated according to data content rules in CCO guidelines.
Date: Date or range of dates associated with the creation, design, production, performance, contractions or alteration of the Work or Image. Dates may be expressed numerically or as free text. The circa attribute should be composed as ca.date. Data values: earliest and latest date should be formulated according to ISO 8601 standards.
WorkType: Identifies the physical type of work being described, ie: paintings, sculptures, installation art. Data values: AAT
Material: The substance or medium used to create the work. Data values: AAT
Measurements: The physical size, shape, scale or dimensions of the work. Data values: use according to data content, for example AACR2.
Technique: Manufacturing or production processes, techniques and methods used to create the work. Data values: AAT
Style/period: Defined style, movement, period, dynasty, school, whose characteristics are represented in the work. Data values: AAT
Edition: Identifying number or name assigned to the edition of the work represented, and its position in the group. For a series or sets, the number is usually presented as a number in relation to other editions. If the data is derived from a secondary source, such as a catalogue, it should be included in the source attribute. Data values: derived from the object or image directly, or from the secondary sources that describe them.
Cultural Context: Name of the culture, people, or adjectival form of a country name from where the work originates. Data values: AAT, ULAN, LCSH.
Inscription: All marks or written words added to the work at the time of production, or subsequent history including signatures, dates, silversmith stamps etc. Data values: derived from the object by direct observation, or from the secondary sources that describe them.
TexRef: Contains the name of a related text reference and any type of unique identifier that text assigns to a work that is independent of the repository, eg: exhibition and catalogue raisonne numbers. Data values: derived directly from the source.
Location: Geographical location or name of the repository, building or site, whose boundaries include the work. Data values: TGN, BHA index, Grove Dictionary of Art.
Subject: Terms or phrases that describe, identify or interpret the work and what it depicts or expresses. Use of a subject authority list is recommended. Data values: recommended AAT, GTN, LCTGM, ICONCLASS, LCSH, LCNAF, Sears Subject Headings.
Description: Free text note about the work, including comments, interpretation, descriptions that give further information not recorded in other fields. Data values: none recommended
Source: A reference to the source of the work, ie: citation in a catalogue, journal etc. The Degree Shows collections in The Image Space, refers to the University College Falmouth in this element. Data values: MLA
Relation: Terms or phrases identifying the related Work and the relationship between the Work being catalogued and the related Work. Can be used to relate Work to Work, or Image to Work records. Data values: recommended relatedTo_ , part of, larger context for.
Copyright: Information about the rights holder, copyright status of the Work. Data values: recommended MLA rules for bibliographic citation for print sources.
Identifier: Dublin Core element used to create a unique number or string to identify the digital resource. Data values: recommends : w_0001 for a work record, and i_0001 for an image record. As we don’t differentiate between Work and Image at the moment, we use the data values already assigned to the digital image, eg: taken from the camera at our shows, or from the Courtauld.