Suggestions and Implications
VRA Core can be supplemented with additional elements, and Zeng offers some notable addition suggestions, including secondary materials, provenance, citations, conservation and structure (Zeng 1999, 1203-1204). The minimal and generic nature of VRA Core and Dublin Core raises questions about the utility of these standards in specialized image collections. Extending these element sets as needed by individual institutions creates serious challenges for interoperability.
There are a number of thesauri and controlled vocabularies for visual information such as the Art and Architecture Thesaurus which uses hierarchically arranged “terminology describing physical attributes, styles and periods, agents, activities, materials and objects” and ICONCLASS, a visual classification system used in art history (Baxter & Anderson). In addition to this, there are controlled vocabularies for names such as Union List of Artists Names (ULAN) and Getty Thesaurus of Geographic Names (TGN). Any metadata scheme for images ought to allow for the explicit referencing of these specialized vocabularies for images so that interoperability is not compromised at the level of the schema.
The hierarchical SEPIADES scheme for photographs seems similar to the EAD DTD, but has the advantage of being part of a framework that includes the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH). A comparative study of the EAD DTD and SEPIADES would be a useful step towards ensuring essential interoperability between EAD and OAI-PMH.
The Resource Description Framework (RDF) and Open Archive Initiative Protocol for Metadata Harvesting seem to have the same goals: metadata interoperability. An investigation into similarity and interoperability of these two standards for their strengths and weaknesses could be the start of a new system that integrates the best features and compatibilities of both.
ISO/IEC JTC1 SC32 WG2 is the Working Group that develops international standards for metadata and related technologies  within the framework of the International Standards Organization (ISO). For example, the ISO/IEC 11179 series of standards describing “data framework, classification, registry metamodel and basic attributes, data definition, naming and identification, and registration”  should be consulted by metadata schema and framework developers. The success of Dublin Core (DC) is at least in part due to the fact that DC is structured according to ISO standards: “Each Dublin Core element is defined using a set of ten attributes from the ISO/IEC 11179 [ISO11179] standard for the description of data elements.”