1. Image metadata: interoperability and exchange
Michael Day UKOLN, University of Bath
Changing Images: the Role of Photographic Collections in a Digital Age, Finnish Museum of Photography, Helsinki, Finland, September 2003
Michael Day is a Research Officer at UKOLN, based at the University of Bath (United Kingdom). Since joining UKOLN in 1996, he has worked on a range of metadata-related research projects, which have mostly concerned the development of Internet subject gateways, interoperability, and digital preservation. He led UKOLN's involvement in the Cedars (CURL Exemplars in Digital Archives) project, contributed to the development of its preservation metadata specification, and produced the Cedars Guide to Preservation Metadata (2002). He was also a member of the international working group on preservation metadata commissioned by the Research Libraries Group and OCLC Online Computer Library Center that produced A Metadata Framework to Support the Preservation of Digital Objects (2002). His more recent projects have included a feasibility study of Web-archiving, undertaken on behalf of the Joint Information Systems Committee and the library of the Wellcome Trust.

2. Presentation overview
Metadata:
Some definitions
Image-specific metadata issues
Diversity of standards
Interoperability issues:
Collection-level description
Integrating retrieval
Object exchange
Some conclusions
Abstract: It is often said that a picture is worth a thousand words – a phrase that perhaps hints at some of the problems of describing images in a way that facilitates their retrieval and use. This is additionally complicated by the extreme diversity of images as a category – which includes, artworks, engineering diagrams, maps and charts, the results of biomedical imaging, multimedia, and much more - and also the technical kinds of metadata required to describe them. This presentation will investigate some of the more generic concepts that underpin image description and will outline various approaches to interoperability between image collections. Interoperability will be considered from three main perspectives: collection-level description, the role of metadata in unifying access to diverse image collections and the physical exchange of images (and metadata) between repositories. The presentation will draw upon a range of examples, e.g. from UK initiatives like SCRAN and the FILTER project and will briefly introduce standards like the Dublin Core Metadata Element Set (DCMES) and the Metadata Encoding and Transmission Standard (METS). A final section will reflect on what interoperability might mean for both institutions and users.
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3. SEPIA Conference, Helsinki, Finland, 18-20 September 2003
Metadata
Definitions:
"Data about data"
About both digital and non-digital objects
Primarily concern function, e.g.:
Resource discovery, retrieval or use
Resource management, preservation and continuing access
etc.
Definitinos of metadata
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Image metadata (1)
Concept-based retrieval:
Based on the interpretation and description of images in terms of what they are and what they represent (Rasmussen, 1997)
Methods:
Free-text 'captions'
Assignment of index terms from controlled vocabularies
Problems with subjectivity and 'aboutness'
Reference:
Rasmussen, E.M. (1997). "Indexing images." Annual Review of Information Science and Technology, 32,
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Image metadata (2)
Different levels of meaning (theory)
Erwin Panofsky - three levels (derived from studies of Renaissance art):
Primary or natural subject matter, forms, objects, events, expressions, etc. (pre-iconographical description)
Secondary or conventional subject matter, … themes, concepts (iconographical analysis)
Intrinsic meaning or content, deals with 'symbolical' values (iconological interpretation)
Sara Shatford Layne - distinguished between what a picture is (objectively) 'of' and (more subjectively) 'about'
Retrieval based on answering the questions:
Who? What? When? Where?
References:
Panofsky, E. (1955). Meaning in the visual arts: papers in and on art history. Garden City, N.Y.: Doubleday Anchor.
Panofsky, E. (1962). Studies in iconology: humanistic themes in the art of the Renaissance. New York: Harper & Row.
Rasmussen, E.M. (1997). "Indexing images." Annual Review of Information Science and Technology, 32,
Shatford, S. (1986). "Analysing the subject of a picture: a theoretical approach." Cataloguing & Classification Quarterly, 5(3),
Shatford Layne, S. (1994). "Some issues in the indexing of images." Journal of the American Society for Information Science, 45(8),
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Case study (1)
Hulton Archive (Getty Images) online search
In addition to a title and caption, each image has a number of metadata attributes, including some of:
Subject (general)
Object (specific)
People (e.g., numbers, type)
Action (the main activities being depicted)
Location (geographical location)
Photographer (name of the creator)
Image Type (e.g., document, photograph, etc.)
Collection (provenance, e.g., "Picture Post")
Picture Attribute (e.g, black & white, layout, etc)
Personality (the basis for a person search)
Natural World (features)
Mood
Setting …
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Case study (2)
Image entitled "Helsinki Streets, circa 1935" (Image Order No. HK8576)
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Case study (3)
Image entitled "Via Veneto, 1945" (Image Order No. JM1531)
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Case study (4)
Image entitled "Archaeological Site, 11th August 1936" (Image Order No. JG9720)
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Image metadata (3)
Initial conclusions:
Need for additional information (metadata) to facilitate retrieval from different perspectives
Image description is not perfect, suffers (like all other human-created metadata) from subjectivity
Language of descriptions a barrier to retrieval
there are some image-specific subject schemes (e.g., Art & Architecture Thesaurus, ICONCLASS) but these do not cover all image types
No realistic alternative until content-based image retrieval (CBIR) techniques are able to identify the semantic content of images
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Metadata standards (1)
Format diversity:
Multiple standards and implementations developed to support different communities and functions
Some examples …
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Metadata standards (2)
Cultural heritage community:
Initiatives include:
SPECTRUM - the UK Museum Documentation Standard
VRA (Visual Resources Association) Core Categories
AMICO Data Dictionary
SCRAN Data Standard
Specific focus on:
discovery; rights management; provenance
Main characteristics of domain:
not only concerned with images; linked with digitisation initiatives; describes objects as well as the images derived from them; some convergence, e.g. with Dublin Core
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Metadata standards (3)
Digitisation:
Initiatives include:
NISO Z AIIM : Data Dictionary -- Technical Metadata for Digital Still Images
Metadata Encoding and Transmission Standard (METS)
Specific focus on:
structure; digitisation processes; rights management; preservation; object exchange
Main characteristics of domain:
fast developing area; many promising implementations in XML, e.g. NISO Metadata for Images in XML (MIX) for Z39.87; modular approaches
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Metadata standards (4)
Geospatial metadata:
Initiatives include:
FGDC (US Federal Geographic Data Committee) Content Standard for Digital Geospatial Metadata (CSGDM)
ISO Geographical information -- Metadata
Specific focus on:
geographical information; spatial data; GIS
Main characteristics of domain:
large schemas; not only concerned with images; convergence of existing standards development on ISO 19115
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Metadata standards (5)
Format diversity:
Inevitable - metadata schemas need to be fit for their purpose (function)
Images are highly heterogeneous
But leads to an increased need for the sharing of experiences (and schemas) across domains
A need for registries of metadata schemas?
Also causes potential problem with interoperability
Three broad approaches to the problem (described here):
Collection-level description
Integrating retrieval and access
Object exchange
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16. Collection description (1)
Collection-level description:
Provides descriptions at a higher level of granularity
"… Can provide an overview of a large number of items, and such overviews may be useful where large amounts of item-level detail may not be appropriate" (Johnston, 2002)
Implicit in many forms of archival description
e.g., ISAD(G) (General International Standard Archival Description), EAD (Encoded Archival Description)
Offers the potential for interoperability at the collection level
References:
Johnston, P. (2002). "An introduction to collection-level description." NOF-digitise Technical Advisory Service Information Paper.
International Council on Archives. (1999). ISAD(G): General International Standard Archival Description, 2nd ed. Geneva: ICA.
Encoded Archival Description (EAD):
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17. Collection description (2)
Collection-level description used in:
RSLP (Research Support Libraries Programme)
Analytic model of collections (2000)
Metadata schema
NOF (New Opportunities Fund) Digitisation programme
NOF Portal
JISC Information Environment
Potential problems:
Differing concepts of what a "collection" is
Uneven implementation
Does it fulfil user needs?
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18. Integrating retrieval (1)
Solves heterogeneity by mapping common metadata attributes (for retrieval)
Tends to be at item level
Main approaches:
Cross-searching (e.g., ANSI/NISO Z39.50)
Metadata harvesting (e.g, the Open Archives Initiative Protocol for Metadata Harvesting)
No need to change the native format of the metadata
Mappings to intermediate formats
e.g. OAI-PMH is currently based on the use of simple Dublin Core
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19. Integrating retrieval (2)
Dublin Core metadata element set
Maintained by Dublin Core Metadata Initiative (DCMI)
Defines 15 element metadata standard designed for resource discovery (e.g., ANSI/NISO Z )
Mission:
Developing metadata standards for discovery across domains
Defining frameworks for the interoperation of metadata sets, and
Facilitating the development of community- or disciplinary-specific metadata sets that are consistent with items 1 and 2
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20. Integrating retrieval (3)
Case study: the SCRAN resource base:
Derives metadata from various cultural heritage institutions in Scotland
Metadata needs to be non-specific enough to be helpful to the non-specialist user
SCRAN data standard influenced by other standards, notably Dublin Core and SPECTRUM
Elements include: Title and statement of responsibility, caption + record details (e.g., Subject, Who, Where, Description, Date, Image Copyright, etc.)
SCRAN has changed its access policies in recent years and it is now only possible for subscribers to see full record details, although a general search that just retrieves 'thumbnails' and basic descriptions remains freely available. The SCRAN data standard is documented in:
Morrison, I. (1998). "SPECTRUM and the SCRAN data standard." mda Information, 3 (1).
Royan, B. (1998). "Cross-domain access to digitised cultural resources: the SCRAN project." 64th IFLA General Conference, Amsterdam, August (visited 8 March 2002).
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21. Application profiles (1)
A concept that allows the local use, refinement and extension of metadata schemas developed elsewhere
Need for registries of metadata schemas
DCMI Registry
"… to promote the discovery, reuse and extension of existing semantics, and to facilitate the creation of new vocabularies" (
CORES Registry (RDF-based)
Reference:
Heery, R. & Patel, M. (2000). "Application profiles: mixing and matching metadata schemas." Ariadne, 25.
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22. Application profiles (2)
Case study: The FILTER project:
Focusing Images for Learning & Teaching - an Enriched Resource (JISC-funded)
Led by Institute of Learning and Research Technology (ILRT), University of Bristol
Project aims:
To encourage the use (reuse and repurposing) of images in pedagogical contexts
To develop exemplar learning objects (cross-domain)
To produce a database of these learning objects and the images used in them
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23. Application profiles (3)
The FILTER project (continued)
Metadata schema
an application profile of Dublin Core
extensions to cover image and tutorial (learning object) specific categories
Database:
Search for images or tutorials
Browse by the highest-level subject categories
Browse by image type
Results demonstrate how the images are used in the context of the tutorial
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Detailed record for an image of Caswell Bay Oolite (limestone) from Caswell Bay, Gower, South Wales. This contains a thumbnail image, very basic details about the file, and (below) more detailed metadata about the image: title, description, keywords, image type, donor, owner, publisher, and a rights statement.
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Object exchange (1)
Interoperability may mean more than cross-database or cross-domain resource discovery:
A need to support:
The exchange of objects between repositories and:
Other repositories
Users
The reuse (and repurposing) of objects
Long-term preservation
Solutions based on:
Encapsulations of data and metadata
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Object exchange (2)
The Metadata Encoding and Transmission Standard (METS)
Digital Library Federation initiative
Supported by the Network Development and MARC Standards Office of the Library of Congress
Origins in library digitisation initiatives
XML Schema
Greater focus on technical metadata than in traditional interoperability contexts, e.g.:
Structural, technical (formats, etc), descriptive, administrative metadata, etc.
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Object exchange (3)
METS (continued):
Modular design - can 'inherit' metadata from other standards (extension schemas), e.g.
technical metadata from Z39.87
resource discovery metadata from Dublin Core, MARC or MODS
The type of technology needed to implement metadata for preservation - METS is understood as a type of OAIS Archival Information Package (AIP)
METS has been implemented by digitisation initiatives in libraries, OCLC Digital Archive, etc.
METS Implementation Registry available:
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Some conclusions
Interoperability standards can help:
Users to find and access relevant information (images)
The main function (for now) may be to help direct users to specific image collections or services
Much interesting development in this area
Institutions (repositories) to exchange objects with other repositories
Fast developing area
Synergies with object management and preservation
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Acknowledgements
UKOLN is funded by Resource: the Council for Museums, Archives and Libraries, the Joint Information Systems Committee (JISC) of the UK higher and further education funding councils, as well as by project funding from the JISC and the European Union. UKOLN also receives support from the University of Bath, where it is based.
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