Why does the protocol mandate a common metadata format (and why is that common format Dublin Core)?
Mapping among multiple metadata formats would place a considerable burden on service providers, who harvest the metadata and use it to build higher level services. While there is research work on creating services such as common search interfaces across heterogeneous metadata formats, a less burdensome and ultimately more deployable solution is to require repositories to map to a simple and common metadata format. The fifteen elements Dublin Core has over the past several years evolved as a de facto standard for simple cross-discipline metadata and is thus the appropriate choice for a common metadata set. Cooperation between the OAI and the Dublin Core Metadata Initiative has led to a common xml schema for unqualified dublin core that is available at http://dublincore.org/schemas/xmls/simpledc20020312.xsd.
