DC-3: CNI/OCLC Image Metadata Workshop

The third Dublin Core Metadata Workshop brought together seventy practitioners in the area of networked image description to address the application of the Dublin Core element set to image resource description. The workshop was co-sponsored by the Coalition for Networked Information (CNI) and OCLC.

The expectation that a set of image-specific elements (an "Image-Core") would emerge from the workshop gave way to the recognition that a slightly modified Dublin Core element set could serve equally well for both textual and visual resources.

Key Outcomes

Expansion to 15 Elements

DC-3 was a landmark workshop: it expanded the Dublin Core from the original 13 elements to 15 elements by making two significant changes:

1. Subject and Description separated — Previously combined, "Subject" now encompasses keywords and controlled vocabulary terms, while "Description" contains descriptive prose or content descriptions
2. Rights Management added — A new element addressing intellectual property concerns, with three proposed values: null (restrictions unknown), "No Restrictions on Reuse", or a URI pointing to restrictions information

The 15-Element Dublin Core

1. Title — Name given by creator or publisher
2. Author or Creator — Person(s) or organization(s) responsible for intellectual content
3. Subject and Keywords — Topic, keywords, phrases, or classification descriptors
4. Description — Textual content description, abstracts, or visual content descriptions
5. Publisher — Entity responsible for resource availability
6. Other Contributors — Secondary intellectual contributors
7. Date — Date resource became available in present form
8. Resource Type — Category (home page, novel, poem, technical report, essay, dictionary)
9. Format — Data representation (text/html, ASCII, PostScript, executable, JPEG image)
10. Resource Identifier — Unique identifier (URLs, URNs)
11. Source — Originating work if applicable
12. Language — Intellectual content language(s)
13. Relation — Relationship to other resources
14. Coverage — Spatial locations and temporal durations
15. Rights Management — Link to copyright notice or rights statement

Images as Document-Like Objects

The workshop reached consensus that images function similarly to text for discovery purposes. "Document-like" status depends on whether resources are bounded or fixed — appearing the same to all users — rather than on content type. This finding meant the Dublin Core could serve as a universal discovery metadata set rather than being limited to textual resources.

A Model for Metadata

The workshop developed a conceptual framework describing the research process through five interactive stages: discovery, retrieval, collation, analysis, and re-presentation. This model acknowledged that metadata requirements vary by stage and that metadata is created by multiple agents at different times throughout an object's lifecycle.

How Images Differ

The workshop identified key challenges specific to image metadata:

• Indexing — text can be indexed automatically; image descriptors are mostly extrinsic
• Encoding schemes — critical for images with numerous format varieties (TIFF, GIF, JFIF, PICT, PCD, Photoshop, EPS, CGM, TGA)
• Rendering requirements — type (bit-mapped, vector, video), compression schemes (JPEG, LZW, QuickTime), dimensions, dynamic range, color lookup tables
• Capture metadata — light source, resolution, scanner type, scan date, audit trails, digital signatures
• Versioning — source images, different views, different scans, various resolutions

Open Issues

• Distinguishing between describing objects versus their digital surrogates
• Collection-level vs. item-level description
• Managing complex object-surrogate-derivative relationships
• Mapping Dublin Core to MARC, FRBR, and image-specific standards

Named Participants

• Charles Rhyne (Reed College) — Chair of Art History
• Jennifer Trant (Arts and Humanities Data Service, UK)
• Earl Henderson (National Institutes of Health) — plenary speaker on the Visible Human Project
• Rebecca Guenther (Library of Congress)